I would imagine that many of these vehicles would indeed be UOR's. As such, they would/should have had a limited Safety Case produced (much quicker to produce than a full Safety Case) that would have allowed quicker transfer in to theatre for use under specific conditions. Risk/severity/probability/tolerability etc all taken into account for its intended (and urgent) use.
However, as is often the case regarding UOR’s, if these vehicles were repatriated back home, not only would it entail the inevitable transport costs as outlined in the first post, but would also attract further expenditure in allowing safe and continued use at home. A full Safety Case including homologation/ legislative requirements, compliancy and of course, the eventual disposal costs would have to be compiled, which may affect the overall picture to the extent that it may be regarded safer and cheaper to leave said vehicles where they are.