I live in Brandon, and I can tell that 3G isn't expected for quite a while, the last rollout happened in Halifax and somewheres else back in February or so and nothing since. Brandon and other decently sized towns should be on the next "upgrades" list, however you won't see 3G along the Trans Can for a few years, and I would be surprised if 3G comes to Brandon within the next 2 years.
Usually when 3G is prepared to roll out, they do quite a bit of testing within a community, sometimes a 3G phone would automatically roll over to 3G service on and off over time, but I haven't experienced that at all.
I also called Rogers customer service regarding 3G expansion and they said that there are no plans for any expansion anytime soon unfortunately. Which sucks