I hope both of you gentlemen know who Professor Michael Byers is: He is a relatively young (I think mid-thirties) professor with law degrees and poli-science degrees who has never lived outside of academia and was a NDP candidate in Vancouver for the last general election. He fully endorses the NDP unilateral "there will never be wars again" agenda, so it's not surprising that he endorses no-submarines policies, just like he endorsed no-F-35 when that issue came up. And BTW, he has not spent a single day in uniform of any service in his lifetime (I don't know about Cadets, though!)
Unfortunately for us, one of his area of knowledge (sort of) is the legal aspects of Arctic sovereignty claims. I say sort of, because he claims certain understandings of facts that he doesn't know or understand.
For instance, his claim that Allies share information on whereabouts of their submarines for search and rescue purposes or to avoid submarines collisions is just laughable.
First, submarines, like any other vessels, are responsible for their own collision avoidance, something you do by looking (or in the case of submarines, listening) where you are going. Nobody tells any body else where its submarines are for collision avoidance purposes, except in exercises, where we do so by setting submarine emergency surfacing areas, for safety purpose.
Second, nobody tells everybody else where their submarines are for SAR purposes: We don't rely on other nations for SAR of own submarines (besides, when was the last time you heard of a submarine SAR ops? I recall a Russian sub about fifteen years ago. That was the last. Submarines in peacetime are not in any serious danger that would require permanent tabs kept on them for "SAR" purposes.
Allied nations, however, do trade partial info on sub operations in two ways: first, area of operations are created and assigned to either submarines, surface ships, and sometimes, MLRPAs. These areas are created so that a surface ship, for instance, that gets a possub contact in a zone where no allied submarine is supposed to be operating then knows it is somebody else's submarine (usually Russian in the Atlantic and Chinese in the North Pacific/Indian Ocean).
The second way to trade info, is if, for any particular reason you are trading joint maritime picture information with another Navy. Then you get where their submarines are.
And Arctic ops, BTW, were highly classified and the info on "who was where" traded only between the two NATO nations that participated: The US and the UK. And no, they didn't tell us anything "for SAR purposes".
So Prof. Byers is completely wrong here.
He is also full of it (since he hasn't a clue on how submarines work, it's not surprising) where it comes to submarines being "available off-the-shelf" and "with the lead time, training to operate them could occur".
First of all, there is no such thing as a "shelf" stocked with submarines (or, as I have explained before anything else for that matter in the maritime world). The fact that some yards have a design of a sub on hand (and built some of them for other people) doesn't mean they "have them on hand". It means they are peddling a design and if and only if they make a sale, start getting the parts they need and working on construction, with deliveries two to three years in the future. That can't help you if you need something NOW, nor may it help you if tension in the world starts rising and everybody (the nation with sub building capacity first) starts to build submarines: You get to the end of the line and wait even longer). Moreover, these peddler of "off-the-shelf" designs may not have what you need (a submarine isn't a submarine isn't a submarine: you need the right one for your circumstances). In fact, as of right now, only one builder makes a submarine that meets Canada's requirement: Kawasaki heavy industries, and they are only now, for the first time accepting to let the design to someone else, the Australian's, in view of their common threat: China.
Finally, his view that you can train the crew during the lead time of construction is simply ridiculous. First, where would you be able to train a sufficiently large number of people simultaneously to take over a whole boat when they all have to start with the very demanding submarine qualification? Second, and this is true of a lot of military specialized fields of operations but even more so in submarines, the problem is never getting enough of the lower rung/beginners qualified. The problem is getting your senior personnel, charged with the more specialized technical requirements and with the advanced tactical knowledge qualified. I am sorry but you cannot take a surface ship CERA and put him down into a submarine after a short two year stint to do submarine qualifications. He needs the lead time of having done his basic quals a long time ago, then served as junior engineer, then as a watch keeper engineer and then as A/CERA all on submarines, to be safe as a CERA. Same goes for sub captains. unless they did their basic sub OOW qual right after getting their OOW cert, then went back as a sub divisional officer, then back as a sub combat Officer and/or XO, they are not fit to take command, and someone who served on the surface ship all his years cannot just step into it. That takes 15 to 20 years, not two or three (and these lead times are getting longer - not shorter). Moreover, the tactical knowledge required is past down AT SEA from submariner to submariner in that osmosis that happens as you serve in ever higher position onboard tour after tour, so that even if you could have the "15 years" lead to send everyone to train here and there in advance at various other nation's facilities, they would not tactically gel as a Canadian submarine crew for years after being put together nor develop a "Canadian" approach to submarine ops for quite some time thereafter.
BTW, Prof. Byers misses one important reason for continuing to operate submarines. Assuming that he is correct and that the defence of Canada's coasts does not require submarines (I disagree, but what the hell, for argument sake), it remains that a large number of nations have and are building even more submarines out there, and Canadian surface ships regularly deploy and operate near these nations. They need the training of facing a real submarine to be able to safely defend themselves, and contrary the good professor's view, nations don't easily "loan" boats to one another for that purpose (in fact, and contrary to what he believes, even the US has a hard time getting non-nuke boat time from allies to train the US Navy - submarines in all nations are heavily tasked, including OWN nation surface force training - so rarely available to loan to others or for extra tasking).

All this would be lost by not having submarines.