I can recall seeing a photo that was taken during the reconstruction of San Francisco after the 1906 earthquake that showed some dual gauge track along the Embarcadro. I surfed the net looking at San Francisco earthquake photos and couldn't find any shots showing the narrow gauge. I did find two photos taken at a sugar plant in Salinas (I thought the narrow gauge was gone in Salinas by 1906). I also found story about the railroad service following the earthquake that mentiond the South Pacific Coast several times. There were several photos of the railroad around Moss Landing but I couldn't tell if the tracks were narrow or standard.
Link to photos:
[sunsite.berkeley.edu]
[sunsite.berkeley.edu]
Link to story:
[www.sfmuseum.org]
I know this doesn't answer Tom's question but I thought it would be of interest to South Pacific Coast fans. Tom, perhaps looking at old photos of the San Francisco waterfront would provide the answers you are looking for.
Jeff Hartmann
RC&BT RR BBQ cook - Summer 1979, Summer and Fall 1980