Perhaps I could shed some light on this... Squarehead was attempting to build a tower, but a stunt plane had crashed directly where one of this walls would have gone, with it's wing stuck in the ground. We tried everything from shooting it to hammering it to destroying the section of the tower around it, but the plane wouldn't budge. I tried respawning the vehicle at Lalam's spawn point (since it was registered to him), but I had no trust with him. After another few minutes, while I was not looking, Square and Star somehow righted the plane (ask them), and on a guess, I hopped on it and flew it away.
Public domain (which had escaped my mind at the time) could explain this all; the plane flipping was the point where public domain kicked in, methinks.