Railroad police certainly is fairly common https://en.wikipedia.org/wiki/Railroad_police. I think that’s because their operation stretches over all kinds of political boundaries.

(Highway police (https://en.wikipedia.org/wiki/Highway_patrol) can have the same role for roads(

Some countries also have special electricity networks for rail, “generally […] only if the railway in question uses alternating current (AC) with a frequency lower than that of the national grid” (https://en.wikipedia.org/wiki/Traction_power_network)