I'm just posting my thought's here.
Can't you connect the shutter cable from xenon HEADLAMP, to the back of the empty pin 6 where the old halogen high beam cable is connected to, using a pin contact?
e.g. make a new cable using a pin contact, filling the empty pin slot #6, and then tap the shutter wire to the new cable??
http://realoem.com/bmw/showparts.do?...=61&fg=15&hl=1