In reply to Jamie B:
As we both know there is no right of access to any buildings.
MBA bothies are maintained and used with permission of the landowner, that permission can be recinded at any time. i.e non of us have a 'right of access' to MBA bothies, we do so with permission.
While entering a building in the hope it is an open bothy (particularly outwith of MBA ones), is both ethically and legally a grey area.