Lee county school system has their own tow truck, store-bought, not homemade. I was kinda surprised when I saw it...we are the smallest county in the state, I don't know how many school buses there are, but couldn't be near as many as other counties. I just wouldn't have thought that there would have been enough call for it. We have several heavy duty tow services in town or close by that can tow a bus.
EDIT: Lee County has 14 schools, 119 bus routes. Figure in a few spare buses, activities/sports buses, etc, and it's maybe 130 buses total. Still seems it would take a lot a breakdowns (that can't be field repaired or patched up) to justify a tow truck.