I really am pleased to read the comments made so far on this new thread that I caused to open. May I ask if the oft-quoted mantra of how the Pacers saved railway lines from closure is really something of an urban myth that is perpetuated by certain people?
I think the discussion is flawed, as of course there can be no definite answer in the absence of documents suggesting a particular outcome was on the cards.
I think in order to accept that the introduction of low cost rolling stock may have saved services and lines, you'd have to first accept that it's not a straight line calculation as to whether a service runs or doesn't, but fundamentally to do with the value that the government of the day places on it.
I'm sure you'll remember the distinctly anti-rail governments of days gone by. The shrinking network, the addition of stops and slowing of services, the ramping up of prices, and so on.
Given the era the Pacers were introduced and the long march of privatisation culminating not long after (mid 80s trains, privatisation started 94). You don't need to be a stock market whizz to realise that either more expensive rolling stock would never have been produced in the first place (resulting in closures), or the loss making lines and services would have looked very different leading up to privatisation. Cuts. reductions, who knows. But it would be contrary to common sense to think it would just be the same but with better rolling stock.
I doubt it was a case that there was a conscious decision to "save lines by cutting costs", but I would be astounded if there wasn't a tight screw put on rolling stock development in order to keep costs down re what I've said above, indirectly mostly likely saving lines from closure in an era when rail travel was distinctly undervalued politically.