I had ordered my car with this option, but Audi forgot to fit it at the factory, so it had to retro-fitted by my dealer at Audi's cost. So it is definitely possible, but I have no idea how difficult it is, since I did not do the job myself. I am also not sure whether the wiring needed was already in place or not.
What you need to know, however, is that there are two different types of sides panels for the left-hand side of the boot in the A1. One version has a 12v socket (which is mounted in a recess, about 10 cm wide and 5cm deep), an elastic belt for holding small items, an LED light unit and a multi-fixture point. The other version (which my car had on delivery from the factory) has none of these "extras".
So, if you want a retro-fit in the original Audi style, plan on buying a new interior side panel for your boot!
I just wanted to say I bought the Audi large trolley case for £250 from Colbornes Audi Dealer and do not regret it! It has been very well made and has served me well as I travel around! Worth every penny