Does anybody know what the diamond and triangle symbols on top of the smokestacks mean?

I spy in the alleyway an electric engine. At first I thought it might have been a GE that also made them for mines, but they didn't match the photo I have on hand to compare. I'm not sure what it is. But more intriguing is the tracks running down the street, which I assumed were for freight. The line has a trolley wire above it, most likely for the engine that is parked. Those used trolley poles.
Mainly, I assume that the power plant powered its own facilities, which includes the switcher. I really like how self-containment used to be done. I image less complaining about far away 3rd party suppliers, independent contractors, and lobbying government for various whatevers. But I can rant (ramble?) for days.

This plant was demolished just a few months ago. During the process riders on the METRO could monitor developments as excavators munched through steel and concrete. At one point huge stators and rotors with their hundreds of pounds of copper could be seen dumped in the mud.

What a great B&W image! That sky looks like it was shot with a red filter, on ortho film.