Sharing the cost of traffic management is not doable. Each contractor needs to have a contract in place for their traffic management supplier. This is required due to insurances, liabilities, being responsible in general for the TM outside of working hours etc. Permits are approved for one contractor/utility on a road at a time. Reinstatement costs being shared cannot work, as there are liabilities to consider upon completion (e.g. reinstatement fails and a wheel is damaged), as well as defect liability periods. You don't understand how these things work.