I found this on the web and it's pretty much what my brother-in-law (a firefighter) said as well. Basically 'truck' people fight the fires and 'squad' is rescue squad and they rescue the people and use the heavy equipment to cut into things (cars, rebar, etc), but they both really do fight the fires and save people as well.
"Fire departments vary on this. As a rule engine companies attack the fire, truck also known as ladder companies raise ladders, ventilate buildings, perform search and rescue, force entry , overhaul, salvage, and more. Rescue companies are generally added in bigger cities, and carry heavy rescue equipment and also respond to fires and also perform search and rescue amongst other tasks. The bottom line is all companies at any given time perform all duties."
ETA: Mesachick...I think we were posting at the same time! :-)
I never knew that "Squad" was rescue squad....it makes it easier to understand now!