What happens is that the model produces what is known as a "ready reckoner" which is given to the bidders.
BBC: Why all the West Coast bids were wrong
2.
This readyreckoner tells each bidder the financial implications of their respective forecasts of how much they think they can increase revenues.
BBC: Why all the West Coast bids were wrong
3.
One very interesting question is how much extra capital First Group and the other bidders would have been forced to hold if the department's model and readyreckoner had been correct.