According to the trade mag, Local Transport Today, the costs of this scheme have risen faster than expected. At £860m, this PFI scheme would not only exceed the allocated budget, it would be more than the Department of Transport's total PFI budget for the whole of England.
Note that while there is concern for the three SEMMS road schemes, including the A6 bypass, other SEMMMS schemes such as Quality Bus Corridors, have already been implemented or are being developed.