Re: Too many "Transit Authorities"? Or, just one fox guarding all of the chickens?
GGT never wanted rail anyway. They are happy to run commute buses, baseline regional runs (equivalent in purpose to SMART), and their Navy.
If you see GGT buses on local runs in Marin, it's because Marin Transit contracts(ed) with them to do it. Sonoma Counxty long ago set up their own transit system, and it seems to work though not exactly luxury-level (GGT might qualify for that, since they are more like Greyhound than public transit). Santa Rosa, Petaluma, Napa, and Vallejo, at least, have their own little bus lines, and Vallejo runs some ferries too. Mendocino Co. has a few buses that make it into Santa Rosa for transfers (yes, you can ride transit buses all the way to Willits or Fort Bragg, with some transfers, but it'll likely take more than 24 hours; better to use Greyhound at least along 101). Then there's SMART.
GGBH&TD is hardly a paragon of decisionmaking, but they have the advantage of a fairly limited scope (the bridge, the Marin/Sonoma commute & regional buses, and the ferries). They seem to work reasonably well within that scope of operation, and are competitive in transit farebox return with BART (which means: pretty good by normal urban transit standards, near 50% most years). I don't think I'd want to turn over all the transit in the North Bay to them, though. Speaking from experience gained from riding GGT in the early 1980s.
BTW, looking the other direction, somebody actually made a trip from SF to LA using only public transit. It can be done. Doing it is probably one of the definitions of insanity ... [archives.sfweekly.com
Yes, there are several Amtrak runs a day that do the same thing, for probably not much more money, in much less time and much more comfort (all but one do involve some bus riding, but they're nice buses). Megabus, Bolt, and Greyhound are also quite available, for a slightly lower fare than Amtrak. And of course if you have a $hundred or 2 for the fare and want to be there in 3ish hours (1 in the air), there's always Southwest/American/United/et al.