I'm all in for space exploration, but this is getting ahead of ourselves. We haven't had a human on the moon for decades, we haven't even landed any devices intended for long-term operation.
Thinking about railroads is like the inventor of the first steam engine planning a highway network. Maybe nice for armchair daydreams, but nothing we should be paying money for.
Assume the equipment scale would be similar to minecarts from an old museum, or some really rich engineer's little backyard train layout.
Depending on how miserable it was to deal with the lunar soil (getting into seals and bearings, contaminating living spaces, quickly developing washboards & potholes on regularly-used lunar buggy tracks, etc), it might be easier to build & use a little Lunar RR for even a <1 year timeframe, even if there was no "moon mining" going on.
Thinking about railroads is like the inventor of the first steam engine planning a highway network. Maybe nice for armchair daydreams, but nothing we should be paying money for.
Smells like pork.