I'd never thought about it till a knee jerk scoffing at the title:
But do they need the TBM to be milimeter accurate the whole way- or do they just need mm accurate surveying and very high accuracy when merging the tunnels?
It might seem inane- but they're two VERY different things.
A lot of industrial and scientific instruments/equipment require a computer to run them, gather data, etc.. Often the software on that computer is Windows based and, if it is, you're not going to connect it to a network (if you can avoid doing so) or use it for anything but running the hardware. OS and software updates are not going to be installed because they'd require software updates from the manufacturer that may simply not be available. e.g. There are still a lot of labs out there with several computers running Windows XP because that's the most recent OS supported by drivers for some very expensive kit.