Quick slightly-on-topic questions: I always read local press releases about how a major local rail or road or stormwater tunnel project "has gotten its TBM" and is assembling it in a portal dug for the initial staging.
It seems that a lot of projects decide on a diameter and then order a TBM for the expected materials that will have to be ground up [sic]. Would it be any significant savings (if you were in Great Britain for instance) to deliberately engineer your whole infrastructure design, and funding, and timeline, to use the exact same diameter as England's High Speed 2's TBM and then run that TBM after they are done with it? There must be a lot of single-use TBMs but I don't know what their builders reuse from one machine to the next.