Technical questions are likely to be commensurate with your flying experience to date. Doubt you need to know any performance figures of any of the aircraft though although if you have the time to get all that under your belt, fine. However just as important as knowing the fleet technicalities, know about the mergers and how this will affect long term strategies for these new/ rebranded airlines. A common question that seems to have come up is "if you were CEO of easyJet (or any other of the airlines) what would your medium and long term strategy entail?" This is a good question to get if you know your stuff - allows you to bring in loads of examples - route expansion, building a brand, upgrading fleet, how you will offset climate change, what new hubs you might like to branch out to......the list goes on and on! I also got a question on what the core differences are between Airbus/ Boeing narrow-body aircraft (fly by wire, sidestick, winglets, engines), and I was also asked why we are seeing winglets on more aircraft today.
Most emphasis will be placed on questions about times you have done things like lead a team, or give an example of..., how would you deal with..... Very important you have lots of examples!