As a general rule (and it's not always the truth) if the majority of buildings are owned by one person/group, that person/group owns the city too. Try scanning buildings, and see what results you get. If they're NPC buildings (and I'm not sure how those come up in a scan) then the city is going to be NPC.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."
If I understand your question correctly, you want to know how you can tell from the galaxy map.
The answer to that is: you cannot. From the galaxy map, you cannot even find out the name of the owner, NPC or not.