A colleague of mine was in contact with Munich regarding this. As far as I can remember he had to prove that his app project would be viable before they would hand over the SDK. I don't know the details but I'm pretty sure that BMW did NOT refuse him access from the get-go, they just wanted to be sure that his project would be useful for the average driver (which it wasn't so it didn't go any further than that
)
What I do remember though is that he said that you don't simply get a couple of libraries in a zip file if you enroll in their developer program, they provide you with a fully autonomous iDrive system to test your developments on. Which might be why they keep this under the radar.
Edit:
Google says
"“Via BMW Apps and MINI Connected, new in-car apps are being rolled out all the time. The BMW AppCenter supplies interested app providers with a Software Development Kit (SDK) that allows them to access the iDrive system and display using A4A (Apps for Automotive) technology.
Deezer, Napster by Rhapsody, TuneIn Radio, Audible and Glympse have A4A built in, which allows these systems to be integrated seamlessly into the driver-oriented BMW and MINI control and operation system,” says Uwe Higgen, Head of the App Center in Munich."
https://www.press.bmwgroup.com/globa...tem=node__5236
You might want to contact this guy Uwe Higgen.