I installed the microphone today. I used the included microphone (vw part). It works fine, but I had to use heated silicone glue to stick it into it's place, because it's smaller than the BMW part. otherwise it works the same.
I tried first to route the mic cable on the passenger side. If you are considering this, DON'T try it. The wire was about 20cm too short, and I realized this just when I got to the headliner part.
So I had to remove it and re-route it on the driver side. The wire was more than enough on this side because:
1) HU connector is on the left
2) I installed the microphone on the left side of the dome light switch
3) on the passenger side you have to go around the glove storage
Works fine now. I have to read to see what the voice commands do
The only problem I still have is the gong volume waaay to loud. I've coded kombi HU_VERBAU to radiostufe_2 for now, hopefully this will use older gong speaker (haven't tested yet) untill I figure out how to lower volume