Device-to-Device (D2D) communications in hybrid networks are provided by identifying a first dual-mode endpoint seeking to communicate with a second dual-mode endpoint via a D2D communications session; identifying a first communications pattern of network resource usage for the first Radio Access Technology (RAT) and a second communications pattern of network resource usage for the second RAT in the heterogeneous wireless network environment; assigning the D2D communications session to the first RAT based on the first communication pattern and the second communication pattern; and in response to detecting network resource usage changes in the first RAT, transitioning the D2D communications session to the second RAT. In some embodiments, the D2D communications session is assigned to the first RAT using a shared frequency regulated by a band access controller that is reserved as a static resource for D2D communication while high-priority signals are absent from the shared frequency.