The helicopter will be used as a transmission midpoint. So the pictures from the bikes/ cars/ whatever is broadcast up to the helicopter which then transmits the signal to a large Outside Broadcast van which then transmits etc etc to Crystal Palace and then to your living room!
There is no camera as such in these helicopters; just a pilot and a hairy arsed Broadcast Comms engineer with a lot of boxes, knobs, dials, wires and copious quantities of gaffer tape. I reckon the BBC would fall apart if it wasn't for gaffer tape!
That may all sound simplistic but it's as involved as I ever wanted to get given I married such an engineer!
Cheers
Whirls