T-Mobile prepaid use in canada?

[Dezine]

The coverage map shows the t-mobile pre-paid covering areas into Canada, in the Ontario area. Does anyone know if a phone will in fact work (actually tried it) in this area with a pre-paid sim? Id like to have this in my Tour because carrying a separate Phone i can use in the U.S. to avoid Bell roaming charges sucks, and I could actually burn off some of the pre paid minutes calling from Canada.