CM:TP progression is D06 > D08 > D05
The hunters make a grand entrance through the DDs which lead from D08 into D05... but the encounter with the hunters "normally" takes place in D08. This should lead us to believe that the hunters are spawned in D05, but since they roam about in D08 without being despawned I think their "indigenous district" or "spawning district" is D08. DDs are always a double set of double doors. There is space between them. Perhaps the hunters spawn in the space between the doors.
You may recall the
Saving the Engineers thread in which I posted videos of brutes being led from D04 into D06. The brutes would despawn in D06, but not until they passed
completely through the DD.