Yes, the green wire is typically mic (+) and the clear will mic (-) in every Audi that I've looked at (C5's, B5's, B6's, B7's etc). Also, the clear wire will feed into a black wire up near the actual microphone. Audi uses a mini-coaxial wire (shielded) for this signal.
I have seen a lot of B6's and B7's with the mic connector near the sunroof...but no mic. It is good to know that you can leverage this connection for the BT mic and not run a new cable. I imagine that you can remove this connector from the panel and insert a few male or female pins on the other side to make the connection....or splicing in works too.
I'm trying to figure out where in the footwell on a U.S. model, the picture above that lt8x7 posted, is located. Being that I have a knack for breaking off the clips that keep interior mouldings attached, I'd like to keep the disassembly damage to a minimum. :?
To help others find the stock microphone wiring harness, I thought I'd take a picture to go along with lt8x7's picture above. To get to the harness in the photo below you only have to snap off the door sill/jamb protector (two metal clips fasten it to the car). Thanks to everyone that helped me get my Bluetooth going.