I believe the siren used is a Whelen Cencom Sapphire. As far as having the siren play when running out of the car there's two ways that i know. 1. Having both ELS and DLS installed will make this feature happen. When i first started playing LSPDFR i unknowingly did this and it gave the siren playing after exiting vehicle effect. However, know that when you activate the siren you will hear dual toned sirens. It gets annoying after a while but if you're into dual tone sirens that alternate just honk your horn and now you'll have dual tone sirens:). The 2. is I believe LSPDFR will auto play the siren if you quick exit the car, however, do not quote me on it since I'm unsure if it'll work. To quick exit you just double tap the button you have bound to exiting (which by default if F on keyboard). I know that there's scripts out there that will purposely cut out the siren after exiting such as ELS siren extender. However for your purposes and what you want I think that trying these two methods will be your best bet.