I wouldn't have thought that VW would offer to fit it. According to my local dealers, it can't be done as each car has it's own specific wiring loom and there are no official VW retro fit looms. The aftermarket kits that many of us have fitted use a third party piggy back loom that plugs between the radio and the cars harness, therefore it wouldn't carry a VW warranty.
I asked the question about fitting a rear camara to my Passat recently. The dealer said it couldn't be done. When I asked why, as surely all the parts should be available. They told me that as it is not an approved accessory and the coding is done remotely via VW HQ, any requests from the dealer for activation of non factory fitted items will not be given.
I think that they are missing a trick here. You can tick all the option boxes you like when ordering a new car, but when you buy a nearly new one, you have to take what's going. Surely they could make more money by offering Approved Used customers the option of specing their cars up too?