I don\'t think I\'ve ever found that to be the case, there are the occasional cop car that drives past, or the odd bike, but I didn\'t see a significant rise in the ammount. All I did when I came across them, was when I found some gang members, back up, and let the car get a bit further down the road, then kill 3 gang members as quick as possible.
If the cops are far enough away, you don\'t get any wanted stars, as soon as you kick off a turf war, it prevents any new cars/bikes/police/peds from spawning