My interview wasn't very difficult. We had a long application, but no resume was necessary. They mostly asked if I had done any EMS work before, if I knew the coverage area well (in terms of driving) and if I had driven an ambulance or large vehicle before.
I wouldn't think you'd need to "study" anything. It wouldn't hurt to know a little about how shifts work (12hr, 24hr etc), and the various stations you would need to travel to, or if that is even an issue.
Since I'm assuming you have limited experience, just be sure they realize that you're eager to learn the ropes and be a team player.
It also may be a good idea to have a clean driving record, but thats sort of hard to fix once something has happened.
I'm assuming this is your first interview, if I'm off the mark on that, I'm sorry.