I got the phone button working with a bluetooth handsfree kit.
All you will need is a steering wheel interface (CAN bus adapter for phone button) and a Parrot CK3000 Evolution car kit. The steering wheel interface includes everything you will need to install into a non-dynaudio B6, you don't have to cut any wires, the kit is plug & play
I have the dynaudio system, so I had to run the audio from the car kit into the telephone input on the factory radio. I used the TELEPHONE KIT - standard radio - STEL from Techmark
I hope this helps.