A managed access system is for mobile wireless devices (MWDs) in a facility, with the facility being geographically within a wireless communications network of a communications carrier. The system may include antennas arranged at the facility, radio equipment coupled to the antennas, a network interface device configured to provide communications with the communications carrier, and a management access controller. The controller may be configured to communicate with the radio equipment and the network interface device to retrieve respective authenticated encryption keys from the communications carrier for each MWD, authenticate the MWDs to a local managed access network based upon respective encrypted keys, provide communications between authenticated MWDs on the local managed access network and the network interface device for communications with the communications carrier, and deny communications between un-authenticated MWDs on the local managed access network and the network interface device for communications with the communications carrier.