It seems logical to me that fire apparatus be paged out in the event of a wreck, but that's just me, and probably due to the fact that my department does that already.

Reasoning:
-In case a fire erupts from one of the vehicles. Safety first, take no chances.
-Manpower.
-Speedy Dry. In my department the fire apparatuses carry the speedy dry to soak up leaking gasoline, oil, and other leaking substances from cars.
-Immediate tools (Oak Cutters, Jaws of Life, ect). I'd rather have these tools accessible as soon as possible, rather than waiting for medical personnel to radio back for it, then send a page out. The loss of time can definitely cost a life.
-More traffic safety. More lights, more apparatus... I feel much more safe when there's engines around rather than just medical personnel.

That's all I can think of for now :X