It doesn't work like that. DfT invites bids for a franchise. It sets the requirements for that franchise, often expressed as where trains need to run and the number of seats/places to be provided at named places and times. They also had quality incentives and, as I understand it, new trains scored highly in terms of the incentives. First Group's role was to offer a bid based on cost of operation (low cost gains points) plus how they might score highly on the quality objectives. They will have evaluated lease costs for existing trains and for new trains, allowing for the fact that there were insufficient trains on SWT to meet the DfT's specification. We aren't privy to the First Group financial evaluation but it appears that the lease costs for new trains was lower than the lease costs for existing trains. From a bidder point of view, delivering the best offer against the DfT's specification is the only thing that matters!