One correction: MMI doesn't list all the registered keys, but it does track them (e.g., you just see the total number registered). I know that dealers can un-register, and I know they're unique.
Neat! Thanks for the additional details. The part I was curious about was the dealership being involved in the process. In other words, who is authoritative: if the car queries the manufacturer for authorization, or if the dealership is updating the car.
http://pixady.com/image/6ds