Very sad news indeed, especially as I live in Vienna. Oneworld will now be very restricted from this part of the world.
I suppose it might be worth booking a few AB TATL economy redemption flights with BAEC, just to lock in the low charges. BA will likely reroute onto AA (main cabin extra) with no additional charges.
Will be interesting to see if the German government finds a way of 'bending' the rules for AB.