I'm not for one minute saying they didn't by the way - as you say, we don't KNOW.
However in my side of engineering it is a completely normal thing to state an assumption that the asset you are altering is in good condition. Old doesn't necessarily mean poor condition if it has been correctly maintained, and unless the client is willing to pay for you to do a condition survey then why would you not accept their assurances that the asset is in good condition? There has to be a starting point from which to estimate a piece of work, and the asset owner should know the condition of their asset!
From a supplier point of view, if I assume that the whole coach will need to be rebuilt and price / programme accordingly then I'm not going to get the contract - plus you will sometimes find that the client will want everyone to price with the same assumptions to get a better comparison of costs, so I could be told to assume that the asset is good like everyone else has.
It's not necessarily the cut-and-dried incompetence on the part of Engineers that a lot of people seem to think it is.
As I have suggested before. It would have been common sense to have a test set refurbished before any contract was agreed. How can you commit to a project you never done before. Scotrail and TS should have figured that out for themselves so I blame them more than Wabtec. Our relationship as passengers is with TS and Scotrail so all the blame has to be directed there. As passengers our contract is our TOC and our Government we have no right to apportion blame to wabtec.
Certainly the Scotland’s best ever railway has not been heard for while. Consigned to the archives and annals of advertising slogans that backfired in the clients face !