I think it depends upon what access restrictions and conditions are stated in the Works Information for a start. If the Contractor has priced his tender based upon an assumption that he will be working in restrictive conditions and the restriction does not actually materialise then it is to his benefit and (hopefully) to both parties benefit with a reduced Defined Cost.
Where such access restrictions are detailed in the Works Information then this can be changed by the Project Manager and treated as a compensation event accordingly, with the likelihood that the Prices are reduced (clause 63.11). The programme assessment under 62.2 and 63.3 only mentions delay, although where any remaining work is altered by the compensation event then this is to be shown in a revised Accepted Programme. Bear in mind also that if a Contractor completes early then this means a reduced Defined Cost for time related preliminaries. That works in theory but in practice they may use any surplus time to retain resources for business reasons.
Because of the likely uncertainty created by the access conditions you describe, I would suggest that the Employer makes detailed assumptions about what the Contractor should price for within their tender and take the risk for any changes, bearing in mind that it is for the Employer to provide details of access in the Works Information.
Where such access restrictions are detailed in the Works Information then this can be changed by the Project Manager and treated as a compensation event accordingly, with the likelihood that the Prices are reduced (clause 63.11). The programme assessment under 62.2 and 63.3 only mentions delay, although where any remaining work is altered by the compensation event then this is to be shown in a revised Accepted Programme. Bear in mind also that if a Contractor completes early then this means a reduced Defined Cost for time related preliminaries. That works in theory but in practice they may use any surplus time to retain resources for business reasons.
Because of the likely uncertainty created by the access conditions you describe, I would suggest that the Employer makes detailed assumptions about what the Contractor should price for within their tender and take the risk for any changes, bearing in mind that it is for the Employer to provide details of access in the Works Information.