El Doctor' --
A couple of corrections for your commentary..

The Fruitvale Avenue Railroad Bridge was completed in 1951 by the United States Army Corp of Engineers.

The Miller-Sweeney auto bridge at Fruitvale was completed in 1973 and replaced the original swing span opened in 1894.
The SP track which the IER had operated on for many years, was shifted from the North side of the "swing span" over to the new RR bridge in 1951..

Regarding the diagonal SP track at High Street which ran from the SP Eastbound Main alongside the scrap yards and down to Fruitvale Avenue, passing underneath the Highway 17 (I-880) overpass structure enroute, THAT screwy intersection only had "crossing protection" on the EASTERN side of the property. Like you said, they were "flashing crossbucks" with 'rotating stop signs' as part of the mechanism--BUT, they never had GATES there !

G