The value of the 25-year deal was initially put at £800m when the contract was awarded in March. The value is now being put at £650m.
The contract covers the upgrade, repair and maintenance of 259 miles of roads and 458 miles of pavements. Work starts in January 2013. Some 200 council staff are transferring across to Ringway through TUPE arrangements.
The initial investment of around £100m will be financed by a bank loan of £88m with a maximum maturity of 24.5 years from BTMU, KfW and DZ Bank, together with around £20m in equity from the project company partners. Remuneration from the council will be based on network availability.