We generally have two ems and two fire drills each month. We like to have at least one of each be a hands on practicals. As far as integrating fire personnel with the EMS drills, it depends on time and what kind of work they have to complete for the fire side.
Extrication once a year, definitely. We get a local junkyard to donate an already wrecked car, put a dummy in it and tear it apart and extricate the patient. The FF's are asked to practice anything they might be asked to do in a real call.
Being a volly station, we can't always count on full EMT response on a scene. For that reason, I like the FF who shows up to drive the rig to the hospital to be able to move the stretcher in and out of the rig, be able to turn on the O2 for me and to know what I mean by "Grab the airway kit, or Monitor and bring it in for me"
We do train all the FFs in Industrial First Aid and HCP CPR. I like practicals to be as reality based as possible. So I occasionally chose scenarios where it's just one EMT and 2 FF, just to get practice dealing with that definite possiblity in the field.