If an alliance attacks an outpost(and wins) will the outpost automaticly be ocuppied by the winning alliance? Or will the place where the outpost was be empty and has to be manually ocuppied?
Yes.
If there is a free place for an outpost, the alliance can occupy it without attacking..
If one alliance wants to take over an already existing outpost, must defend its owners. Therefore, the victorious alliance takes over the outpost.