Hello,
There are a couple of Mobile Phone connectivity options available on the C6 A6......
The GSM factory fit comes with the front arm rest connections and Bluetooth. However, there is also a bluetooth factory fit which was only available with MMI High and does not have any front armrest connections unless the optional wired privacy handset was spec'ed with the car.
(Data taken from October '07 A6 Sales Brochure....)