It does seem kind of silly to put the panels between the rails, more prone to damage there from stuff falling off the trains, derailments, etc. and not angled for optimal sun exposure though I guess it's easy open space.

Before I read the article I was thinking the electricity from the panels would power the trains but doesn't sound like the output is enough.

They're getting 180 watts per meter, so it would take 50 km of panels to power one high speed train. And that's when the sun is shining. Double this at least if you want to store the energy and run trains in the evening.