Yeah right, think about it logically...if you have a capitive audience, you'll try and eek as much cash out of their pockets as possible. I have no doubt that BAA have, much like any other airport, a commission structure for concessions...so what is the point of bringing in the mighty M if their average yield per head is much lower than other possible concessionnaires and, hence, less commission in the BAA coffers.
Let just hope the alternatives can push through the bulk custom which M's inevitably always achieve...