Earlier quoted context omitted.
According to a quick google, noticing that other cars are pulling in/slowing down usually works if they can't see the emergency vehicle. Still, it's not "perfect", but then Hearing drivers are far from perfect either, and there's plenty of failsafes before an accident happens.
Fire trucks and ambulances I've seen when driving against traffic lights/flow of traffic always slow and stop to make sure that there will not be an accident even if they have the right of way - they don't drive like police in pursuit on TV. I'm sure there are exceptions but the general case is the emergency vehicles are planning for other traffic to not yield until it is clear the other traffic is yielding.
Yes, if the driver is well trained. When I was firefighting and instructing drivers, we always emphasized that while the red light and siren gave you the right of way:
a. they don't absolve you of liability for a crash (at least under NC law)
and
b. if you get in a crash on the way to the scene, you're not doing anybody any good, PLUS you've now created another incident requiring another emergency response, PLUS another company (probably coming from further away) has to respond to the original call.
I can't speak for police, but firefighters are actually, in my experience, taught to be pretty conservative when it comes to running red lights, proceeding against traffic on one way streets, and other similar scenarios.
We also always used to emphasize "it does no good to get halfway there, real fast".