Not all information is stored on the key fob. Only service relevant data
However the car will log plenty of data BMW HQ can retrieve if need arises.
The dealer does NOT have access to this data and can't intercept or read it
BMW HQ for example has used the data to verify abuse after bend valves, burned clutches etc...
So bottom line is anyone who puts any kind of tune on their cars (sw, piggy back, paper clip , whatever)
has to understand they MAY have to cover costs for repairs and loose their warranties (if it's a lease car BMW can even possibly have you buy out the car as you breached the lease agreement)