Not quite sure what the "mirror link activation document" sold by Amazon does...
I would guess that somewhere in the menus there is an activation screen, into which you type in a one use code that then (using the GPRS datalink) connects to Volkswagen over the internet to validate and activate on your car...
A bit like using a prepaid card for your Xbox subscription...
On the other hand, i think it should be possible to hack the same functionality locally... if I had a MIB2 I'd give it a try, but i don't... MIB2 should be quite readily hackable I think you will find. MIB1 only isn't because its a pain to get the network connectivity up, MIB2 takes away those problems.