Comment by mitxela

Their 100 y/o hardware is built from stuff that's still produced though. We still make relays (not identical ones but ones that perform the same function), wires, and mechanical levers. The system's behavior is not encoded in the relays but in the connections between them. If you had a CPU made of separate transistors you could replace burned out transistors with any future transistors but if you had one made of chips you'd need those exact chips that were out of production.

Replacing the relays in old telephone switches is a problem because they use so many weirdly specific types of relays - but those systems are only found in museums now. I believe track control uses fairly ordinary DPDT, etc., relay designs.