Activists are concerned that a deal struck by the Marin General Services Authority more than a year ago may have cut off county bargaining power with telecommunication companies ahead of a new federal rule limiting local control of 5G cell networks.

Those networks, which are designed to provide high-speed internet at least 10 times faster than 4G, require the placement of small-cell antennas throughout city infrastructure, attached to fixtures like streetlights and utility poles. Because…