Some quick input on needing the FZD. Dealerships use the software service station (SSS) as you all know from reading posts here. The software is somewhat automated in that when you do a software update or you do a retrofit it scans all of the modules and their data and then comes up with a "measures plan." It also reads the Vehicle order or "VO" from the vehicle which is basically a list of all of the option codes of the car, the pro date, the region etc so that it knows what software to install. Obviously it needs to know if it has nav, etc so that its not trying to program a module that doesnt even exist in the car.
That being said what will happen when you have an incorrect module in the car or if a module is missing it will come up with a measure plan that will say "replace xx contol module with xx part # and then restart. Basically the SSS locks you out of doing any programming or retrofitting until it sees the correct module in the car.
When doing a retrofit for the bluetooth what is going to happen is the SSS is going to modify the vehicle order to reflect SA639 which is BMW assist. Once it modifies the VO it will then determine a measures plan to program/encode all the modules that need to be updated in order for the assist to work properly. My guess is what is going to happen is it will scan the module info and see that the FZD is incorrect and lock out any coding until the proper FZD is installed. I have done a couple of these retrofits but I have always installed the correct FZD. I have never tried it with the old FZD, therefore i cant confirm for sure that this is what would happen but from experience common sense tells me that it would. If this is the case then its not the saavyness of the dealership or the tech but just the fact that their hands are tied by the equipment.
With best Regards,