It will be fine. The only downside is that since the meat has been cooked and reheated, it will have some of that reheated flavor. Luckily, bbq brisket does not suffer from this as much as most beef for some reason (I think because of all that added flavor from smoke, bark, etc).
I have started many briskets on the smoker and finished in the oven with no problems. I don't think I've ever done precisely what you did however, but again, I see no reason it shouldn't be just fine!
