The spec is not very explicit about how the container should determine the routing region and subscriber URI to be passed in the call to getNextApplication().
The AR should not have to duplicate this data into the stateInfo field of the result.
Instead the container should be responsible for propagating the region and subscriber URI between calls of the AR including in the case of a ROUTE_BACK.
For ROUTE BACK the container should add 3 parameters to the pushed route
- the Subscriber URI
- the Routing Region
- the encoded content of StateInfo