How can you tell who the owner of a city is on planet? I see plenty of empty cities around and would buy from someone if they don't want to build on it, but don't know who the owners are.
____________
"A diplomat is a person who can tell you to go to hell in such a way that you actually look forward to the trip.”
The only way I know of is to request to build a facility, and see who the request goes to. Of course that requires you to be there. Do note that often people will lay cities intending to build on them later (Gand, for example, where I have slow construction plans in progress), so they're not necessarily willing to sell.
____________
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."