Earlier quoted context omitted.
tangentially related bit of trivium... when i was house hunting a looked at a house across from a fire station, and upon doing research about what it's like to live across from one, found that a.) they tend not to blast sirens upon exiting the station, in contrast to living near a hospital with an ED, and b.) the power grid segments that fire stations are on have priority and are less likely to lose power during blac…
I wonder if the siren thing varies from location to location, a good friend of mine lived right next to one and it seemed you couldn't go 15 minutes without being drown out by them heading out.
In my experience (former firefighter here), it absolutely does. It also varies by call type, time of day, etc. So if we got a call at 2:00 AM and there was no traffic on the road near the station, we might leave the station with no siren out of respect for the people trying to sleep in the homes very close to the station. This would be more true if the call was a lower priority call in the first place. OTOH though, if the call as "residential structure fire with occupants reported trapped" our focus would not be on sleeping neighbors and there's a better chance that we'd be getting on the Q pretty much right out the door.
Another factor for us was that our station was right next to an intersection that was very busy at times, and known for many traffic accidents. So any call where we had to turn left (towards the intersection) out of the parking lot, there was a better chance we'd be hitting the siren and air-horn pretty much right from the jump.
Anyway, yeah, net-net, this is going to vary based on lots of factors: department policy / culture, geography, time, traffic, etc, yadda yadda.