1. Yes, Vzn does have coverage up there, since they basically built the CDMA network that Telus uses. You will be charged extra for International Roaming, but use it sparingly and you'll be fine.
2. You can get a North America plan that gives you coverage in the US, Canada, and Mexico, anywhere that your phone gets a signal. No extra fees, but you will have to pay like $60/month for a lot less minutes (no unlimited N/W, no M2M, etc.), and since it's a totally different plan family from what you're probably on (America's Choice) it'd require you to restart your contract to get onto it. Not very ideal for a short trip.
3. If you happen to have a GSM phone, and it's fairly up to date, then yes, buy a prepaid SIM card when you get up here. I honestly wouldn't know who to go to for that though, I've only dealt with US carriers. Usually convenience stores and electronics stores (Brick, Future Shop, etc.) would carry such things.
4. You could also invest in a very cheap prepaid phone, like $60 or so for a Virgin Mobile Canada phone (they have different plans/phones up here from Virgin Mobile USA), if you're going to be in Toronto for a month or two. I'm pretty sure it's a standard PCS phone, so when you're done you could sell it or keep it, whatever.
