NEC ECS: Instruction de-scoping work - do I terminate a Subcontractor or follow CE process with them?

Been instructed by the PM to de-scope and provide a quote which for one supplier means in effect their termination. Should we follow CE procedure with s/c or just terminate under cl 90?

You have to follow the correct contractual processes you have with your Subcontractor in accordance with the contract you have with them. If an instruction to you removes the specialist equipment they were going to install and they are no longer required, that sounds like termination to your Subcontractor. This will be a compensation event to you with your Client, so any costs you are going to incur as a result of the termination will still be recoverable to you as part of your compensation event with your Client.