VdG
As I said I did not want to get involved with the purely AAR considerations because that is not my field. However, I must challenge your saving of 13 billion. People tend to forget that this figure covers the whole of the programme from procurement to operation of the aircraft over 25 years. You would certainly have been able to buy your KC10s for considerably less than this figure but would still have had to service and support them. All of this aspect is also covered by AirTanker within the overall headline figure.
Having said that I long ago questioned the wisdom of PFI programmes especially where the capital cost is extremely high. The balance between capital and service delivery has to be right, as it is on the service delivery that the theoretical efficiency savings pay for the higher cost of finance for a commercial company (typically about 2% higher than the Government can borrow). I am not convinced that this balance would be achieved in the Voyager contract although AirTanker and its backers (shareholders and banks) obviously are.