This very well could be the Orinda area.
Though what caught my attention is that the equipment fits the description of the Sonoma Magnesite Copmany's RR that ran farther North between Duncans Mills and Cazadero. It was a very short lived 24" gauge railroad and I know of no photographs of the railroad in operation.
It's only claim to fame is that long after abandonment a fellow by the name of Erich Thompson went up there and scraped a fair portion of the track for use on his 12" gauge railroad in Oakland's Tilden Park, which is a stones throw from Orinda.
I'm wondering if the equipment, which I've never read the disposition of, some how ended up in Orinda and that's how Erich found out about rail.
Sorry I couldn't help,
Curtis F.