So we have learned that the new A3 8P and A4 B7 have a gateway which allows to exchange information between the three CAN busses (and the k-line?). Without this gateway newer CAN-only devices (like the phone interface) aren't accessible via VAG-COM, probably because the CAN at the ODB plug is not the same CAN the phone interface is connected to. This issue seems to be present in thew A4 B6 when trying to get the phone interface retrofitted.
So, is there anybody out there who knows if this CAN gateway is retrofittable? Or at least how it looks like and where it's connected to? Worst case it might be part of the insturement cluster because this piece is already connected to all CAN busses.