This is the actual use case for a number of European countries who have a phased approach for the rollout of new network services where a dual device is a requirement supporting both Tetra and 3GPP LTE services.
In essence they will continue to use Tetra for mission critical voice and an MVNO initially to provide the 4G/5G data bearer services , assume will be non mission critical bearer services i.e. QCI 6/7.
The next phase would be to build their own private LTE network again this would offer data services only with reliance still on Tetra for mission critical voice services the data services would be mission critical QCI 69/70.
The final phase after a number of years and one would assume after a hell of a lot of testing would be to switch fully to the LTE services with both voice and data once the network has matured and proven stable at this point there would be no further reliance on Tetra and the system could be decommissioned.
It seems only the UK has gone down this route of relying on a commercial network operator for radio access , this than integrates with the ESN network.
Biting the hand that feeds IT
