Air Canada does have interline agreements with QR (see http://www.aircanada.com/en/travelin...ket/index.html) and their policy *is* to allow you to check bags through whenever they have an agreement. If the agent you're checking in with is reluctant you might politely push the issue and insist that you've been advised they can and ask to check with a supervisor etc. You should make sure to keep the bag tag and probably even show it to the QR agent in YUL to make sure they accept the bag.

International flights are almost never canceled even if they're several hours delayed whereas domestic flights are sometimes canceled when bad weather there's bad weather. I would avoid YTZ (and the smaller prop planes on YYZ-YUL) and stick to the larger jets.

It's true that deicing in YYZ can add 40+ minutes even when things are going well and up to about twice that when there are problems.

You might consider flying in earlier in the day and planning to get a taxi or bus into the city centre and back. There must be things to see or do in Montreal in January that would make a nice contrast to Doha