1. Police really don't want a shoot out (especially not a high speed one) in a populated area. Air support is for the most part for spotting and getting ahead of fleeing targets. The ground forces deal with the actual assault. They are also very hesitant to shoot down an airplane over a populated area. For that, they have drones that can attach to the hull of a vehicle and then detonate on command. Usually, they'll let you get to your destination or a roadblock provided and then close the noose.
2. Earlier editions have vehicles but you'll have to convert. There's Rigger's Black Book and Rigger 3 (I don't have #2) Also Fields of Fire had some stuff and Corporate Security Handbook had the Ares TR-55 series. NAGRL had DocWagon vehicles, but those got included in Rigger 3. In 4th I think there is Unfriendly Skies and Deadly Waves with flying and water based vehicles respectively.
3. Standard responses were listed in a couple books, but they were admittedly fast. Realistically, it would take a while for response, but for the sake of the action, they were listed in initiative passes. If you're looking for realistic, do your own research. If you're trying to squash a combat, use the listed numbers or just pull a "The cops just happened to be patrolling just now." card.