Build_and_Break:
I can't assume all railyards have towers at those positions or that they have interfaceable power.
This is beginning to sound like a problem-for-every-solution.
Presumably you could install a small tower with batteries and solar panels or a wind turbine to charge them. I see solar panels and small wind turbines on the UK rail system.
What about adapting one of those wheeled carts that is used to support a temporary lighting mast?
...R