My local MB dealer in Newport Beach CA, Fletcher Jones, did not charged me for brake and coolant flushes when I had my car in for second A service early this week. Gillybenztech wrote very clearly about these two items a couple months ago that they are covered under Maintenance Commitment plan for model year 2000 and newer US cars.
http://www.peachparts.com/shopforum/showthread.php?threadid=54588
Also, if you read 2 small books in owner's packet: Maintenance book and Warranty book, you will see that they are paid for by MBUSA. Show your service writter these books and Gilly's writting, demand that they bill MB for brake flush when you bring your car in for B service.