All they do at the running in service is change the oil. The fact that power is electronically limited prior to the running in service is an urban myth. The engines are very tight for the first 5k miles though and are much more responsive once they've loosened up a bit - especially if they are run in properly. Far too few owners read the running in instructions properly and floor it after the 1250 service. It takes 3,000 miles to run in an M engine and the idea is to build the revs and top speed GRADUALLY between 1250 and 3000 miles.
The only time the car is limited is when it is in "transit mode" between the factory and the dealer - it has electronic restrictions and suspension blocks in place to protect the springs and shocks and has a very low limited speed to stop the guys taking them off the boat and transporters at high speed and ruining the suspension!
Tim