Slightly surprised (but I will go and do a review) that you feel there is more than one school of thought on the principle of this answer as I think our experts will have a common answer to this. It may be that there are subtly different questions on a similar theme that might give rise to subtly different answers.
The intent of the contract is that the Contractor can only claim for additional resources as part of the CE quotation. If the existing team that are full time on that project can deal with that event then there is no additional cost incurred. The only exception I would say to that is that if you had a resource that would have left the project part way through, but now they are staying longer to do that CE then that could be claimed for. The problem you would have there is proving it. As a Contractor I always used to submit a resource schedule/release plan so they could see what resources I had planned throughout the project. This made it easier to justify where staff are being kept longer as otherwise it was difficult/subjective to prove.
I take your argument about that staff could have been utilised elsewhere but that is a practical or moral argument not a contractual one. The problem is if a Contractor could claim that cost for every CE, they could be doubling/trebling/quadrupling their staff costs they can claim for every CE compared to the actual resource they will have - which would not be fair on the Employer. You could argue what the contract says is not fair on the Contractor, but I think on the scale of fairness that is more closer to fair than if the Contractor can claim staff cost for every single CE that are running parallel with each other.