The stats people under the contract are 'Others'.
Put them in your programme with reasonable periods given what you do know. If the PM wants you to change this pre-contract based in better information, then that would need to be reflected in your Prices.
If they clarify/ change it post-contract signing, then it would be a change to the Works Information.
If the stats people don't work to the timescales in the programmes, it will be a compensation event. Providing you have done what the Works Information requires in terms of liaising, accommodating and providing traffic management, the delays will not "arise from your fault", so you should get compensation.