Jack, Shandon Iron didn't have anything to do with Diamond. The reason I asked is that I ran Shandon Iron for a number of years, before it closed.
I'm real familiar with the Diamond folks though. Those trailers are as maneuverable as heck.
When they leave the plant/headquarters in Shandon, they go through Ross to get to the Freeway. In Ross they have to go through an odd intersection. In the pic below, they would come from the left side, and then make the 'jog' an go to the upper right. I stopped at that gas station every morning for coffee, a donut, and a can of cat food for the junkyard cat that I had named dCon. Every now and then I would see them come through that intersection and it was always neat to watch.