It looks like we got everybody - that is every commuter railroad in the bay area.
Locally, there are a couple of usenet groups that are marginally useful. one is ba.transportation - and it can be pretty nasty at times. (One of the regulars grew up in my home town, and stole a Budd RDC and drove it into the turntable pit, a few decades ago - that'll give you some warning.)
The other is sbay.transportation - hard to find, except on the old www.deja.com
(now google groups). At one time, there was a "gentleman's agreement" allowing "technical" discussions of non-sbay (south bay = south of San Mateo bridge - State Route 92) transportation. That has gone away, but the archives have some pretty good technical resources.
The new groupings look good here, thanks Otto!