Rando Marmotte Alps

Hello.
Anyone know how the Rando Marmotte works with regard to accomadation and overnight bags etc.
I've done the one day event several times but I'm wondering about the logistics of staying in Valloire for the night when you started in Bourg that morning. I heard something about busses with trailers for bikes but wondered if anyone has experience of doing this.
I also notice on the website that there is a luggage transport service (only for rando participants)
Cheers for any help on this.