Exactly right karrie, between lack of competition, the lack of existing infastructure and the enormous cost/benefit ratio of providing towers in Canada, it can make for a sticky situation.
For instance, Rogers
still has zero coverage between Kenora and Thunder Bay, because the amount of money needed to build those towers far exceeds what they could ever reap from selling service to a total population that is less than 40,000 people (in an area that is encompasses more than 70% of the province's geography). On top of that, the area there is so dense with bush, lakes and the Canadian Shield that it would take far, far more towers in order for cell service to be available there, and even then the service would be sporadic. The only reason they have any cell service at all is because they purchased the older, used analog towers that southern Ontario was getting rid of on their way to upgrading to the newer digital ones - to say the service there is shat would be an understatement; communities such as Atikokan would welcome a digital carrier like Rogers with open arms.
In America, if one company provides infastructure for an area, the service can be used be all companies utiliziing the same technology; because of their huge population and the competition that it creates, that can be easily (and cheaply) done. But here, because companies like Bell, Virgin and Telus refuse to use the easier, more reliable GSM technology, we have to erect twice as much infastructure just to give people any choice at all.