That was me! Yes, I did it on the Atlantis. It was excellent. I snapped my derailleur in half at the bottom of the descent out after Prineville, single speeded it 70km until a nice fellow sold me the derailleur off his bike after calling it a day. I was looking for other Riv's, didn't see any! Were you in the parking lot at the start?
I also saw a number of fendered bikes. A number of guys I rode with had them actually. One was a custom bike with 42mm Compass tires (rear tire was slashed and destroyed right where my derailleur died. He had a backup, which was later slashed as well!), the other was an Elephant with the same tires. They were pulling mud out of them fairly often though. Oh, also there was a Nobilette-built Velo Cult rando bike with honjo's. It was gorgeous.
I'll be posting a full report in the next few days, just need to decompress, download the 1,200 photos I took... and do a write up. Also, my Atlantis never arrived on the plane with me coming home... I'm hoping to find out where it is today.