The difference to me between MT and the ATU (GT/CT flavour) was mostly that in CT, your adventures were about local things (by local, I could mean a few planets or just a small ship or small area) and the characters mostly were chasing after their own goals and solving modest mysteries and so on but in MT, the setting literally cried out to be the focus of missions, adventures, etc. and where the Rebellion background would actually be the foreground instead (the Rebellion would overtake most petty concerns).
If the SPA is responsible for all Imperial starports, that would logically include E types. Would they have an office there? Or would they simply have some signs posted identifying the site as an extrality and the a jurisdiction of the Imperium as administered through the SPA?
Starport E: A perimeter fence with some flat-ish space identified on the local site survey as 'landing pad' and appropriate signage indicating the extrality zone as being under Imperial Authority. Otherwise, there may be nothing there...
TomB