The way it works as this. The coding computer determines what ECUs (Electronic control units) on the car need updating based on their current configuration. This is why, in some cases reprogramming a BMW can take almost 8 hrs if a large number of ECUs need to be reprogrammed.

So by installing say the sirius receiver, although the technician will go through the retrofit procedure, its certainly possible that other ECUs will get reprogrammed during the procedure.