Looking at pictures of these Police cars it does not look like they had sirens
Added: I believe that they used alarm bells or "military horns" (alternating high-low pitch)
Police cars have sirens.
To warn other cars it is coming through!
Yes
the sirens tell people that a car is coming also it sends a signal to stoplights for a go.
yes you can press the circle button when driving the police car
The french police drive terrible cars with terrible sirens were as the Miami police department drive good cars with good sirens, also they have a better way of processing people and information in the Miami police department. Also, the Miami police probably need better training, because Miami is the most crime-filled state in the US.
Policies and laws vary from state to state, but in my locality, police officers basically use sirens (and lights) any time they are responding to an emergency call. If they are responding to a silent alarm, they may choose to not use sirens, but that's not common around here.
good cars
not very
bmw
ugly cars
I don't think you can. It's a shame! But you can use a police car and turn the sirens on by pressing the right analog stick; cars will move out the way.