I have been in Montreal for a few months,..and I will be keeping my US phone.
I pay an additional $40 per month for unlimited data with Sprint and thats on top of the simply everything plan $99 I think.
There is also a Canada add-on for $4.00 per month that makes the cost per minute 20something cents instead of 50somethiing cents.
I stopped into Bell canada,..and they tell me that i can get a sim card from them,..drop it into the TP2 and I can get HSPA 3G speed and pay month to month.
still not sure what i am going to do about a Canadian phone,..almost bought an iphone from Bell the other day because I am so frustrated with HTC TP2,..but then I remembered that I am a MAN who likes the ladies,..and i wont be caught dead holding that fruity girl phone.