I've also seen parallel trolley wire for brief stints on the San Diego Trolley, and it seemed to take the place of a frog. However, that wire is parallel and not over-under like in this photo. Unlike street railway wire where streetcars used shoed or wheeled poles, pan wiring is greatly simplified.

Any casual comparison of Los Angeles Railway or P.E. overhead compared to interurban lines that used pantographs like the Key System, Sac Northern or in this case CSS&SB, would see the obvious advantage to pantographs. Note that pan overhead does not need frogs or other expensive hardware, and that the accuracy can be greatly reduced as the pan shoe can slide around, whereas a pole will pop off if the wire is not so perfect.

I can't be certain about the second messenger on the left of the bottom picture. Several years ago, I saw a photograph of this setup, I think it was back east, and when I asked about it the answer was that it was designed for maximized leveling with the hangers in effect being twice as accurate in height due to the greatly reduced variance, which allowed for high-speed running. Think CNS&M and the IC electric. Maybe even other interurbans were set up with this? Like CA&E, Iowa Traction??

Ohio Brass was a significant vendor of much of the hardware found overhead.