You can find all kinds of interesting emulator implementations out there. I’ve personally seen a large manufacturing shop run some of their core business processes inside DOSBox.
https://www.youtube.com/watch?v=zWJZFQHklBg
No need for emulation when the original equipment is still working.
I worked with a large factory running all their lines and processes off an emulated, embedded controller. It was running on a desktop PC using NT 3.51 interfacing directly with real-world I/O.