In the Port Landing card it states that you can use it to bring down troops to Neutral or Friendly areas.
On the game board it says that the Traitor player can move units from Terra to either area of the Vengeful Spirit using the Port Landing order. It doesn't state whether these have to be Neutral or Friendly.
Thus, can the Traitor use Port Landing to move troops from the Landing Pads to the Vengeful Spirit into areas occupied by Imperial troops and fight a coexistence battle there?
Allowing such a move would make counter-attacking any incursions into the Catacombs very easy indeed, since Port Landing is a 1-initiative card even when executed from the hand.