Yes, it is. Before the evaluation process at the European Commission (EC), both evaluators and observers have to sign a contract with the EC that specifically includes a confidentiality clause as well as well as a no conflict of interest declaration. 

They are required to commit themselves by an “appointment letter for independent experts” (based on the model given in Annex F of the “Rules for submission of proposals, and the related evaluation, selection and award procedures”), stating that they will conform to the principles outlined therein and will follow the rules and procedures set by the EC. This includes keeping all information gained during the evaluation process confidential and not retaining (or copying) any materials that pertain to proposals or the evaluation.