Prevent the theft, don't just deter it through legal consequences. Increase perimeter security (barbed wire, electrical fence) so that it's harder to get onto the rails in the first place. Keep trains moving - don't park them for hours in dense metro areas with poor perimeter security. Get better locks.

Or, partner with Mark Rober to create a giant train-car-sized glitter bomb that will douse thieves in glitter and fart spray when entered.