BMW e46 Factory Bluetooth with aftermarket radio.

[toyink]

Hi Guys,
I'm new to this forum. Wondering if anyone has ever attempted to make their factory bluetooth telephone system work with an aftermarket radio.
My car is a 2004 e46 coupe which has a factory bluetooth preparation installed.
After removing the business radio/cd player and retrofitting a Kenwood double din navigation monitor, I found that the bluetooth still works but I've lost the tel speaker function and there is no way of displaying the phonebook and number dialled on the aftermarket system.
I've narrowed it down to 4 radio connections which are Mute, Telon, Telnf+ and Telnf- on the radio plug wiring loom. Is there anyway I can purchase an interface or form one that would translate the function performed by these outputs to my Kenwood system? I think it would be in the nature of an av-in av-out type adaptor/interface.
Or perhaps I'm asking too much?