On my sportback the inside part of the rear light cluster (the part in the hatch) is only used for fog lights and reverse lights. The other day I was behind a new sportback that also had the inside part lit with just the normal lights on (like on the A4). In my opinion this looks a lot better. I did some searching and found this: http://oooo-a3.blogspot.com/2005_11_01_archive.html Take a good look at the pictures in that article!
It appears it is just a question of some VAG-COM coding to get the inside part of the cluster to also work as regular rear lights. The mentioned post deals with getting rear fog lights to work in the US and only mentions how all the bulbs in the rear cluster(s) operate but does not specify how to do the coding. I have VAG-COM, but I have no idea what setting I should be looking at. Has anybody ever done this? Or even better: Does anybody have this behaviour by default (I am guessing it may be set like this from the factory on the latest cars). I would love to know what your (long) codes in VAGCOM are. I think I should be looking at module 9 (centr. elect.)
Edit: I may have found the correct settings.
In VAG-COM Module 9:
Byte 9: Brake Light left/right Rear as Parking Light (US Standard: 18%, EU standard 22%)
Byte 10: Extra Function: Rear Fog Light left/right as Parking Light (US standard 12%, EU standard 0%)
So it looks like in the EU the brake light is used at 22% and the fog light is not used at all while in the US both are used with the brake light at a slighty lower setting (presumably to keep things from becoming too bright). I'll try it out in the weekend.