@foone You may be underestimating how weird the diesel part is.
https://en.wikipedia.org/wiki/EBART extends an existing BART line with 9.1 miles of track, using diesel trains and standard gauge track. It has just a transfer station and two new stations. This was not existing track or anything, it was built specifically to extend an existing line, because it's apparently cheaper than electrifying a 9 mile extension?
Want to go from "Pitsburg / Bay Point" to "Pitsburg Center"? One stop, but change train.