Communications between smartphones with Mission Critical Push to Talk (MCPTT) on public safety LTE Networks including FirstNet built with AT&T, Southern Linc's CriticaLinc, Verizon's Push to Talk Responder, and other LTE networks, and Land Mobile Radio (LMR) subscriber devices is called INTERWORKING. Interworking is an essential element for the deployment of these LTE based services, for both the migration to LTE from legacy LMR radio networks and to augment LMR radio networks with new LTE devices. One solution to LMR LTE Interworking is through the 3GPP Standard "Interworking Function" (IWF), however this solution only addresses P25 LMR networks with the ISSI/CSSI interface, and may be months to years away. Meanwhile, Interworking using Radio over IP, Radio Control over IP, and other connection technologies have been deployed, and will be the prevalent choice for non-P25 networks and P25 networks without an ISSI/CSSI interface. The early deployments of these interworking solutions provide useful insights into the challenges, successes, and feature sets of these interworking solutions. In this session, end user organizations and the vendors and carriers that provide these services will describe these initial installations. What's required to put interworking solutions in place? How do they work? What's the current capabilities of these systems, and what s on the roadmap for next generation Interworking? Hear from an end user, an interworking vendor and others as they discuss the early implementations of Interworking, and what we've learned.