I have found the following in a forum: "Le seul cas ou le mobile est remplacer [sic] en agence FT est une panne sur stock lors [de] sa mise en service au moment de l'achat" (FT = France Télécom). Source
http://www.forummobiles.com/topic/179270-orange-conditions-d...
The distinction from a PMS seems to be that the phone proves faulty when - instead of being taken away for less than 30 days as in a PMS - it is tried out at the shop and there must not be more than 30 minutes' calling time on the "clock".
Hope this helps.
The translation workplace 
