Allen,
Yeah, the phone in the cabin we stayed at wasn't even as deluxe as the one pictured. It had the old school separate receiver with transmitter mounted on the front of the wooden case.
Not surprised about Pacific Telephone's reluctance to upgrade service in remote portions of Monterey County. Ma Bell didn't think it was worth the trouble, and they were probably right. Residential service has always been a losing proposition. After the Bell System breakup of 1984, the newly named Pacific Bell was really pushing products and special features, which in your case was a dedicated line! When I worked for Pac Bell, the old timers all said that Pacific Telephone was the ugly stepchild of the Bell System, so the party line service you described isn't at all surprising.
I'm pretty sure Seneca's system is still autonomous, with no connection to the outside world. That place is so small, it would probably be faster to just yell from your front porch.