Just had a thought on those LA "Drills", that main drag and all the connecting side streets had to been block off from both vehicles and pedestrians, there is no way the military would bring those choppers in that hot without making sure no one would be in the way. Must have been local PD helping with the blocking, I know there are websites where you can listen to fire, rescue and PD radio transmissions, some of them record the chatter for replay latter.
Here's one of those online scanner feed websites, this link is for LA
https://www.broadcastify.com/listen/ctid/201