Can an expert organisation be part of a consortium from the application stage, for example in partnership with a municipality? If so, will it be considered a co-beneficiary and co-signatory to the sub-grant agreement?

Yes. Expert organisations can formally participate in a consortium from the application stage, as long as all members meet the eligibility criteria. the sub-grant agreement is typically signed between the ERR and the designated beneficiary, which may be one legal entity (e.g. the consortium leader or a newly established REC), who takes legal and financial responsibility for the project vis-à-vis the Emilia-Romagna Region.
While the roles of consortium members can be described within the proposal, only the designated beneficiary will be a signatory to the sub-grant agreement. Any internal arrangements between consortium partners (e.g., work-sharing, subcontracting, internal MoUs) must be handled contractually by the beneficiary in compliance with applicable rules.