It's one of the reason trains get stuck in Europe: thieves stealing copper cables. They've been found to steal, too, heavy road grate if they were of any value: which created actual serious accidents (where a car's tire falls into the hole).
Regarding the electrical cables for trains, one solution is, slowly , replace them with cables with basically the same properties but 1/10th the copper.
Other funky solutions have been implemented: chemical sprays with a composition that is watermark and that cannot easily be removed. So when caught the thieves cannot deny because for x weeks the watermark stays, invisible and harmless, on their skin.
One question of course is: what does society think we should do with thieves who create road accidents and who render trains inoperable?