They want to open to the public and will do one day somewhere but they have had many, many problems.
They have moved premises 3 times and recent years and eventually arrived in Chelles with great enthusiasm and hope. That was 2 years ago and they were originally offered the large ex Sernam wharehouse adjacent to the main Paris -Est trunk and TGV line. There was even serious talk of using part of the redundant sidings at Vaires gare de triage for running rollling stock including trams and metro vehicles.
I think the Sernam offer has now been withdrawn and they are stuck in a redundant wharehouse near MacDonald's that is too small and useless for a museum. Half of the exhibits are at another location to the north of Paris.
Chelles is an expanding conurbation and I expect that development land is more important financially than transport relics.
I do hope that they can get some better support but I think that French bureaucracy and lack of long term commitment is also the root of the problem.