I did a bit of googling to see what the various state, provincial, and federal agencies had to say about bear and dog encounters.

Manitoba says this:  "Dogs can serve as an early-warning system for the presence of bears but should be kept on a leash at all times. If an unrestrained dog confronts a bear, the bear may follow the dog back to its owner."

Ontario this:  "It is important to keep dogs away from a bear. While a well-trained dog may deter a bear, a poorly trained one may only excite it resulting in the bear following the dog back to its owner."

  (You need to Login or Register is fairly interesting.  Don't bother if you're on dial-up, however.  It doesn't say anything about what to do with your dog, but I think they cover that elsewhere.