I don't know if it is BMW certified - but I always bring my cars to D&V Autobody in Sterling, VA. They work on quite a few exotic cars in the area (sometimes for custom paint jobs and such). I've unfortunately had to bring cars there a few times due to accidents and the cars have always come back looking great.
A lot of other car enthusiasts in this area take their cars there too.
http://www.dandvautobody.com/