OIC. In that case no, because we all knew it sometimes got left on so standard practice was to shout "anyone in there?" in that case. With the red neon grabbing attention, it is now unlikely to mean anything other than 'occupied'. Of course there may still be the odd cry of "OI!!!" from within when a thoughtful passer-by turns it off. However, if in doubt its simple enough to just try the handle; we do have one of those feeble lockable handles.
An "Occupied" indicator was never my criteria, "Occupancy" (not the same thing) was raised by the PIR fans, I just pointed out that the indication is a bonus with the red neon.
Phil