They may have a helicopter of sorts.
The real camera car is actually a go kart in which the stig can reach a top speed of 200 MPH
Alot of the time the super-fast cars are actually only going about 40 mph for those scenes. They don't need a supercar to keep up with that. Notice how there are no lightning-fast mega speed follow cams.
It's a Land Rover Discovery with the back door off. :P