The guy who flew past you in the SUV must have been known as an off duty cop ...or his brother. Whereas you , Vin, are just a FD guy.
Seriously, the whole "speed limit" thing.. both the stated limit, and the enforcement of, are just a loose attempt at helping traffic flow w/o scaring gramp's off the road. ....and a big bit of revenue for some.
The guys w/ sirens do of course believe that they get special rights . ..because they do. It's that we all know that allowing cops to speed is the only way that that they don't become super anal about the "limit" that they "enforce" (as a tax). --they get to pick a random driver, give a ticket as evidence of "hey, let's slow it down to posted" and then they get to speed away to the next hit. --maybe fair in it's mostly randomness. ...different cops, with different chips on the shoulder.
Of course that all will go away soon, and we'll have the cop replaced by automated super-anal traffic ticket cam's. --enforcing with ease, all of the arbitrary low speed zones, as well as ticketing cops.
(unless cops and FD's are above the law, they too will get ticketed for speeding ...even to an emergency. --After all, if above a certain "limit" is deemed unsafe, then we certainly can't have anyone exceeding that limit. ...for ANY reason.)