There is more to fire departments that just fighting fires.
Fund Raising: Bingo nights, and little carnivals, and Community Feast/All you can eat buffets.
Station up-keep, a lot of cleaning and washing fire apparatus and equipment. Some fire departments in California even make their own ladders (at least they did 20 years ago).
Fire Prevention Education.
CPR training for the public.
Fire Department Banquets: Big parties departments throw in appreciation of firefighters and EMTs.
There could be a fire academy where sims go to train to be firefighters and EMTs.
Emergency Medical Services: Taking ill sims to the hospital. EMTs could fight with the Grim Reaper over dying sims.
There are many types of calls Firefighter and EMTs run that are not fire or sick/injured people related. Cat/kid stuck in tree, Car accident, ect...
Plus you could add a lot of little items that people want, but are not big enough to warrant their own pack.