Your not supposed to know this, but you can pick up Sirius in almost all parts of Canada, because of the altitude of the satellites. The only exception is that it's spotty in the upper reigon of Canada. They don't "officially" offer service in Canada, so if you want it, you will have to drive across the border to purchase a system, and then activate it with a U.S. address.
Check Siriusbackstage.com if you have additional questions.
Someone was supposedly looking into licensing XM for canada, but I don't know if that ever went through... I'd be more doubtful of them though, as that would probably start to get to extreme angles if you go too far north...