I haven't seen any posts about TdF sightings so I thought I'd mention that there are some :-)
In today's stage (#17, Bagnères-de-Luchon → Peyragudes) there were a few on the penultimate climb (Port de Bales, about 38km from the finish).

And if you need a little extra dose, here's a gallery of camper/bus photos I took last year:
http://nextchapter.kraikerphoto.com/2011/07/buses-of-le-tour.html

Regards, Peter Kraiker
nextchapter.kraikerphoto.com
Toronto, ON, Canada
'82 L Westfalia 1.9 TD 5 Spd (Babe)