I wonder if that was slowed down, while they consider how to best integrate it with the P25 system that Fort Worth/Tarrant County is building? Northeast Tarrant, Arlington, Mansfield, and Grand Prairie are all listed as participants in the planning, and NETCO (Northeast Tarrant) is shown on the 'map' on page 9 as being in 'Zone 2' of the proposed new system.
So, that brings up the question, will Northeast Tarrant function as a part of the future FW/TC Public Safety P25, or remain independent. Similarly, Arlington, Mansfield, and Grand Prairie are lumped together in Zone 3 of the new system. As already discussed over on DFWScan, the new system Johnson County is building will be linked to FW/TC for interoperability purposes, though not a direct part of the system.