In reply to jethro kiernan:
When I did it last year the route was almost a loop, so we were expected to make it back down the mountain on our own steam (20km or so, downhill all hte way back into Annecy) which was probably the only sensible option open to the organisers.
The year before I did a more traditional point-to-point one - you buy a navette ticket when you register, drop your car at the finish line the day before and get the bus back to the start. This happens most years I think.
The website says this too in their FAQ section:
CAN I LEAVE A VEHICLE NEAR THE FINISHING LINE?
There is a shuttle service available on the eve of the race, allowing you to leave your vehicle near the finishing line. Saturday, July 19th 2014, between 9am and 6pm, shuttles will run regularly from Argelès-Gazost to Pau (host village). Shuttle seats must be booked in advance at the time of registration.
Therefore, you can leave your vehicle near the finishing line and return to the host village with the shuttle.