'Provide the Works' is a defined term – see clause 11.2(13). It includes ‘all.. incidental actions which this contract requires’. An ‘incidental action’ the contract requires is for the people to travel to work and that will include incurring congestion charges if they travel into or through the congestion zone.
This cost will therefore fall within item SCC item 13(a). Equally it could fall within 13(i) or 13(n). Whichever it falls within, it is incurred to provide the works, as is defined in the contract.