I had a good look today as we got airborne from Bordeaux and there are actually two Mercures there.
Both are on visible on Google Earth to the north of the runway intersection. The first is shown facing south in a group of four aircraft (inc a Caravelle) and the second is a little further to the NNW and looks as though it might actually be outside the airport boundary.
The first one is in the Air Inter blue striped colours and the second is on the later white fuselage scheme. The first has either suffered from a starboard main gear collapse or it has been parked on soft ground as it is leaning to one side.
The one that you think 'might be outside the airport boundary' is with a training school called the IMA - see
Ingénierie et Maintenance Aéronautique - IMA — UFR de Physique . There are a few pictures of some of their aircraft, but none of the Mercure.
It is indeed 'just outside the boundary' ... just a few feet across a narrow road that runs around the fence. The Mercure is outside their hangar as it is too large to fit inside.