The suggestion in today's German newspapers is that IAG has bid for the routes and fleet associated with the Vienna based Niki subsidiary. This is presumably the same focus as the bids from easyJet and Niki Lauder + Thomas Cook + Condor. However they are also reporting that Lufthansa and easyJet have been selected by AB as preferred bidders, with no word on the IAG bid's status.
Air Berlin had about 140 aircraft, of which 30 were in Niki. Lufthansa has apparently bid for 80 or so aircraft and equivalent routes, which suggests most of the shorthaul network. If this was the UK, Lufthansa would face a competition challenge if there were other serious bidders, and all the alternative bidders wouldn't face this barrier. Germany's aviation is not a "contestable market" from my perspective, even with AB alive.
Niki mainly serve Austria, Germany, Greece and the Iberian peninsula, to simplify somewhat.