Thanks Splitmike. Indeed in Germany it´s a fairly straightforward process, you can even order the plates on the internet and have them delivered to you. The Germans are clearly more used to foreigners buying cars from there and importing them themselves.
Austria is a different matter altogether. There is very little information on how to apply for export plates, and only in German. In the end, it´s as simple as contacting one of the insurance companies that double as "Zulassungstelle", they provide you with the plates and insurance, so it isn´t that difficult after all. Be aware that the prices are pretty hefty though.
I know that many people (especially Germans) do buy theír Californias from Schweiger in Austria and pick them with German temporary plates. It´s cheap and simple, but it has a BIG drawback: you end up driving an Austrian car with German plates, so you´re actually not covered by the insurance. It´s up to each and everyone to decide if they´re willing to take the risk, I think it´s just not worth it.
Hope this is useful for anyone considering importing from an Austrian dealer (Autohaus Schweiger most likely). Incidentally, the dealer didn´t really have much idea about the whole process, apparently they´re just to used to people resorting to German plates. Otherwise they´re very recommendable.