A lot of it is dependent on the signal quality as well as site preference in programming. Certain signal strength thresholds can trigger checking peer sites for better signals. Additionally, preference can be programmed for specific sites. In the example you are talking about, the Bridgeport campus system was probably built to reduce the overall loading on the G system. The radios were probably programmed for site preference to the Bridgeport sites. That way if the signal strength is above the threshold to check peer sites, the radio will favor Bridgeport simulcast. As long as all of the system-affiliated radios are on the same site, there is no need to use resources from peer roaming sites and those resources remain available for others.