A method and system for managing backhaul capacity between radio access network (RAN) infrastructure and a plurality of base stations providing coverage areas in the active set of a wireless communication device (WCD), where each base station has a respective backhaul link with the RAN infrastructure. An example implementation of the method involves determining separately for each base station a ratio of a quantity of control data to bearer data on the base station's backhaul link, determining that a given one of the base stations has the lowest determined ratio of the determined ratios, and responsively transitioning to a restricted mode where control data communication with the WCD occurs via just that base station and not via the other base stations, but bearer data communication with the WCD occurs via all of the base stations.