Bell’s transitioning to an HSPA network is no secret. As such is the case, the Canadian carrier is making sure that everything is all ironed out and ready to go, including US roaming, once they roll out nationwide coverage later this year.
In line with this, they've inked a deal with AT&T to serve as their official roaming partner south of the border which is a good indication that their moving full steam ahead with their plans. Interestingly, though, Bell seems to have the upper hand in the agreement. While AT&T subscribers in Canada using Bell’s network are limited to HSPA-enabled networks only, Bell roamers in the US can access both AT&T’s HSPA and legacy GSM network.
This, in turn, gives us an idea on what Bell’s new GSM line-up of phones could possibly look like: mostly 3G/HSPA capable phones with several GMS/EDGE ones on the side. Likewise, we’re now also doubting the rumor of the iPhone 3G S coming to Telus as it now looks more likely that it will become available on Bell soon thanks to this new AT&T-Bell partnership.
[source]