This policy brief presents a framework for enabling cooperation between government authorities and Citizen Observatories (COs) in urban environmental monitoring and policymaking. It outlines approaches for overcoming key social and technological barriers — including data quality assurance, interoperability, and inclusion — using CitiObs tools such as the FILTER methodology and the Leave-No-One-Behind Toolkit. The brief emphasizes the importance of shared data infrastructures, open standards, and participatory governance, and proposes dedicated institutional structures and co-creation spaces to support sustained, inclusive citizen science at scale.