If there is an ambiguity and the project manager has to make a decision to correct it, how can the project manager decide whether it constitutes a compensation event under the ECC? Does the project manager automatically have to take the position that the contractor had made the lowest cost assumption during the bid?

Answer

If the ambiguity exists in the works information, the project manager corrects this ambiguity via a change to the works information, (clauses 14.3 and 17) which is a compensation event. It is then assessed as if the prices, the completion date and key dates were for the interpretation most favourable to the party which did not provide the works information, see clause 63.8. Therefore if the works information prepared by the employer is changed then your assertion is correct.