Interesting question. I don't know the answer. If it works it will probably cost 59¢/min. Of course, you'll need to have a phone that does UMTS on bands 2 and/or 5. Canada discontinued all 2G GSM several years ago.
I messaged T-Mobile Customer Care online and they said it should work, and that texts would be $0.10 and voice would be $0.59/min.
I visited Canada and shortly after crossing the border, my phone connected to Rogers and I received 2 texts (labeled "Free T-Mobile Msg") explaining:
- Text $0.50 each
- Talk $0.59/min
- For more info, call +1 505-998-3793
- Charges are up to $15/MB+tax for web/email/apps while roaming.
- To disable data, dial #763#
I checked my balance and I might have been charged a small amount, even though I didn't use the service.
I think I was mistaken and I was not charged a small amount.