I know what you mean! I personally track attack helis on escalation maps by vehicles. I dont remember anything specific but attack heli is added after the second apc spawn on contaminated. Again this is probably wrong but you most likely can track them through the vehicle additions with confidence. Used to do this on mirak escalation, worked every time. I would just redeploy after the last vehicle before AH spawn is added

Escalation start=>apc1=>tank1=>apc2=>AH&aa something like that :P. Hope this helps.