The answers I seem to have come up with range from absolutely nobody besides Canadian citizens and resident aliens of Canada from UBC and Calgary, to “we haven’t accepted any in the past 6 years, and won’t unless they are clearly superior to Canadian applicants” from McMaster (that 6 year track record doesn’t exactly encourage one).
Natalie, from your thread elsewhere it seems like graduuating outside Canada and going there to practice is next to impossible as well.
Guess I may just have to wait till my next life to live in Vancouver. 
My reply is mostly based on information about the main school I'm looking at in Canada, but I know that McGill University in Montreal does encourage US applicants. Of course, if you're looking to live in Vancouver, that doesn't really help. I would call the admissions offices of schools in the area you want to be and find out from them what their policy is. It seems that the rules are often more stringent for out of province Canadians than for US students, but that might just be my experience. Nothing hurt by asking.
As for receiving your degree in the US and then practicing in Canada… Once again, from looking at McGill, they state that it's no problem to receive an MD there and then go back to the US to practice. It seems that rule should be reciprocal, but I don't know if that's actually the case. I believe what Natalie was referring to was trying to practice outside of the US as a DO, as opposed to an MD.
Be sure to post anything you find out, I would be interested to know some more answers myself.
Good luck my fellow future Canadian!