It's obviously not 180 kWp/m. If it was I could put 1 meter of panels on my roof and power my house and 200 of my neighbors.

I didn't try to calculate the amount of energy it produces in a year, just the length of panels required to power a high speed train when the sun is shining. 18,000 watts / 100 meters is 180 watts per meter. At 180 watts per meter, 50 km gives you 9 MW, which is about what a high speed train consumes at cruise.