Given that I went back and forth from St Jean to Ottawa frequently for a year (say 2 times a month, roundtrip) and that I still use the same method to go to Montreal, heres the info for ya:
If you have a student card (and I believe they give military the same discount anyway, so) it is 40$ round trip. Might as well buy a roundtrip ticket, if you want to come back. Otherwise, it is 20$ plus tax.
Full price is 60 plus tax, (divide by two for the one way rate).
Tickets are all open ended. I have a feeling the military would just ask for the receipt and pay y ou back for it, rather than buy the ticket for you, but then I dont work for a CFRC.
You take the bus from Ottawa, (either the bus station or St Laurent Shopping Centre, but bus station is a better idea) and it lets you off at the Central Station in Montreal.
You then get onto a metro, (2.75$) and take it to Bonaventure station. You walk up the escalators, and you will find your way to the Communter Bus Terminal.
You grab the 9-something... cant remember exactly, but its the only one to St Jean, and I believe its between 6-9$ cash (cant remember as I bought a booklet). The bus stops at the mall in St Jean, and you taxi from there.
(note that this is the "i make no money" route)
Or you can just taxi from the bus station in montreal, skipping the metro and commuter/city bus.
(this is the, "I have mommy/daddy's cash to spend or someone else is paying for it" route.
)
You can also substitute in a flight/rail if you wanna spend more cash.