Hi Aerofoil,
I did the assessment last week and there was a mix of low hours non TR like me upto a Capt on the 757 with 11 years experience etc....
My understanding is I think you will still have to go in the 737-200 sim, and the interview is mainly based around the aircraft you have flown, in your case I would expect questions on the 737-300/900. If you have any queries with it though email the guy at EMA, he is very helpful and am sure he would confirm this either way for you, they will not think badly of you for trying to confirm what is expected of you on the day.
Good luck with it
Dan.