The likelihood of a bear invading your BBQ pit are directly related to how the wild prey situation is. Like most wild animals, they prefer to avoid us humans and our turfs, if they have a plentiful supply of food in the wild. There are the few rogues, but for the most part, wild animals would prefer to avoid us, as much as possible.
That said, anything can happen. It is all about probabilities. If the bears, and other critters, can find food in the wild, they will probably not take any risks to get the food off of your HOT smoker.
Desperate animals, like desperate people, do things they wouldn't normally do.