> Thankfully, Switzerland has lots of meters of railway.

The linear meters of railway are nothing compared to the square meters of rooftops. Putting panels in a long row is the maximally worst arrangement you can come up with.

> There's caternary on 99% of Swiss rail, every few dozen meters, that already transmits power.

I guarantee this wasn’t oversized to accommodate power transmission duties, too.

It’s also high voltage line. The solar setup would need additional and expensive high voltage equipment to interface with the line and to work within the design parameters of a line that was designed to deliver to the train, not carry extra power.

You could put the panels anywhere else and connect them normally to the grid like every other installation.