In regards to overall availability, winter warfare is pretty much a done deal if you spend much time in an infantry trade. We've got lots of winter to spare, and a lot of experienced staff ready to provide training. Even if you dont take an official course, it can be written off by senior staff as 'completed' after you have completed a winter training exercise of suitable length and had appropriate training sessions during that exercise (however, that was a while back so not sure if that practice is still allowed).
Jungle warfare is a bit tougher of a nut to crack, as it has to be on a course outside of Canada (no surprise there). There are only so many slots available, and unless you are lucky, or have some mission, unit, or person of influence supporting your nomination, you're unlikely to get it.
Even if you dont get the jungle course, there are still a lot of other interesting courses out there to take, dont build your future career around just one concept...