The Contractor realised after the quotations were accepted by the PM that Contract Data Part 2 recommended CECA rates for plant, the Contractor used less favorable rates in his quotation and now would like the sum in the accepted quotations to be revised. Should the PM consider this request?
In short - no, assuming the event has been “implemented” under clause 65.
Had the Project Manager realised when he assessed the quotation that wrong rates had been used (high or low) then he should have assessed accordingly, but once implemented there is no recourse to revisit a compensation event for either Party.
Would the Contractor give back money if he had realised afterwards that he had used rates that were too high and agreed within the implemented CE? It is the same rule/benefit/dis-benefit to both Parties. The idea of compensation events is to agree them and move on. They will not always be perfect, but better that than save them all up to the end and have a big (subjective) bunfight.