tbaytel's coverage in Thunder bay far exceeds Bell/Telus's. They have no service down the highways, whatsoever. Once you're about 20 mins out of town, you get zero signal. Tbaytel covers you all the way from the manitoba border to Sault Ste. Marie, down to the border down highway 61. There will be small gaps, but Bell/Telus gives you nothing.
ROgers also has 2G fallback in Kenora and THunder Bay.
As for CDMA, Telus roams off tbaytel's CDMA network, which is actually quite good and covers all the aformentioned areas.
Now, I'm not sure Telus will give you an 807 number if you need one. But as of right now, Rogers is still the best way to go if you need coverage in northwestern ontario.