Also, how can NO LIMITS own a world wonders build site on an island where they have no cities at all? How can we take a world wonder site? We will own the island in a day or so.
So. I believe it is fixed now. My alliance was occuping a cnstruction spot on the island with 8 our cities. Now all of them we conquered by other alliances and we do not occupy that spot any more. No one does.
On the other hand I see a spot on the very next island, which is occupied by an alliance, that has no single city on it. How it is possible? Simple - there was a bug, which allowed an alliance to occupy a spot even though this alliance did not occupy the whole island. So they booked the spot. Now this should not have happen, since you can not start occupation of the spot if you do not controll all cities on the island.
There are 2 ways how this spot can be free:
1. the alliance conquer the city on that island and lose this city afterwards.
2. the alliance will get disbanded.
Long story short - prebooked spots problem is solved now. But the result of the bug will still be in this world for some time: some spots will stay occupied by alliance, that booked it when they have had no single city on that island.