They will talk about systems, I suggest you be able to draw them. Even in training programs which don't require that you memorize schematics I do it anyway because it makes it a lot easier to understand and talk about.

Airliner systems are a lot more complicated than a 172 so if you can't even explain 172 fuel, electrical systems you will probably not get hired.

Also take a look at the turbine pilots manual (any pilot shop)...read a little about turbine engines, hydraulics, and PACKs.

I have heard of CFIs getting asked RJ systems questions...I hope that was a mistake and they got confused with an applicant who was ex-121. But if that happens, politely remind the interviewer that you have never flown a turbine aircraft. At that point you will get bonus points if you have done some turbine background reading.