This doesn't seem like it would work. Debris falling off the trains, dusty buildup, vibrations, rocks bouncing around the tracks; heck, even just wildlife crossing the tracks. So many things are gonna damage those panels if they're just lying on the ground between tracks, and solar panels are extremely fragile.

I hope they have some sort of bullet proof glass or something over those panels. Probably going to need a special train to spray water over them to clean regularly, too.

I dunno about Swiss trains, but the tracks behind my house in America leave a thick black film on everything, and it's very hard to clean by hand. I think they transport coal.