its actually safer for the ambo to navigate around you if everyone is already stopped (and they are more likely to get into more trouble if they don't know if a car will move or not). A lot of the lights in the cities can be controlled to switch through their cycle quicker if an emergency vehicle requires it. (and some have the inbuilt frequency thingy that makes the lights change for them.

Although if the ambo was tooting, I would probably try to turn left with care (esp if there is a green arrow) regardless of the direction I was going in)