Considering I know someone who has been involved in franchise bidding recently...
You assume I don't.
...the general feeling is that unless you propose new stock in your bid you don’t stand a hope of getting the franchise.
Obviously I'm not a regular poster on these forums, but I do read them a fair amount. In general I find that this site has lots of very well informed commentary. A notable exception to this is the mythology surrounding how DfT award franchises.
It is really not that complicated - they publish an ITT on their website for all to see, and when they receive the bids they stick rigidly to the evaluation criteria described in that ITT. If they just chose the bid they liked the look of because it had shiny new trains they would be taken to court by the losing bidders.
Some franchise bidders have proposed refurbished trains and have lost franchises to other bids who were bidding mass new train orders.
I'm not familiar with the bids you're referring to but I would be very surprised if the choice of rolling stock was the clinching factor for the winning bid. Far more likely to have been the premium. The weighting on the rolling stock bid plan is not that high when you consider the premiums that were bid in the last five years (the weighting on quality score is not a fixed element so it diminishes when the bidders are bidding high premiums - look up MEAT in any of the ITTs).
It's also important to bear in mind that when DfT are scoring bids, the rolling stock score isn't just based on the type of train proposed to be used - it's also about lots of boring detail like day-to-day management, asset maintenance, depot provision etc. Again, read the ITTs. The upshot of this is that an excellent management plan using rolling stock refurbished to a high standard cannot score significantly fewer points than an excellent management plan with new trains.