I think getHideFrom returns the point where to hide behind an object to be hidden from a unit.
I've always seen [0, 0, 0] returned, so I dropped working on the command, but now I see setHideBehind (this command had skipped under my radar), perhaps in fact getHideFrom returns the position where unit should hide in the hiding object model space.
It doesn't really explains why I always got [0, 0, 0] as result, though