I don't know the specifics as I said earlier, but if you have an instrument rating already then I would guess you could be asked to show your skills in this area. I have also known with other operators that they will give you exercises to fly such as climbing and descending co-ordinated turns IFR, e.g. rate 1 turn from say North to South climbing 1000ft to check out your IF scan.
All I can recommend is just be ready for anything. Even if they give you a hold or a procedural approach it may not be for where the simulator is located or even where you might be expected to work.
Just take it as it comes.
Whatever you get, good luck.