Can't give a specific driver a ticket from an airplane. I thought the main function of the planes was to follow extreme speeders, which has to be revenue negative -- just because there are so few and it takes so long -- but maybe a justified expense.
They are able to identify speeders without radar using fixed distance marks on the road and timing cars traveling between those marks. At that point, they are then able to give information about the car to the police on the ground for them to be pulled over.
These days they all pretty much have systems like the Churchill/Shotover Augmented Reality Mapping System (ARS) which will give them target vehicle speed automatically. Even news helicopters use similar systems[1].