First, you should know that the cadastre is not “very” accurate in the mountains. But it seems to be better than the original import of the “CIA world” db anyway
Second, you should know that we have some conventions about administrative boundaries in France and we would appreciate if you could follow them. The cadastre is about the municipality border - admin_level 8 - and is a relation aggregating several ways as it is demonstrated here: http://wiki.openstreetmap.org/wiki/WikiProject_France/Tracer_les_limites_administratives#La_m.C3.A9thode
It becomes particular when the boundary way belongs to more than an admin_level which is the case of a national border. In this case, the way belongs to the relations of the municipality (level 8), the département (level 6), the region (level 4) and finally the country (level 2). For the country, we don’t have a single relation since we have too many ways. Therefore we have sub-relations for e.g. all ways between France and Spain, another one for all ways between France and Germany, etc. and one super-relation collecting all those border relations together. If you modify the border between France and Spain, you will have to modify all of these relations excepted the super-relation.
Last, about your question of the source, you have to replace the AAAA by the year of the last update of the cadastre on this area. For this, you have to go to the original site www.cadastre.gouv.fr, open the “Vue d’ensemble de la commune”, clic on “S’informer” on the left panel and then “Editer les informations relatives à cette feuille” on the bottom panel.
Usually the year of last update is either 2008 or 2009.
Following that I would move defective “CIA” border for about 50 Km in Central Pyrenees. I would maintain the tags but changing the “source” by something like “Yahoo aerial imagery, public domain cartographical references and personal experience”
Finally I have finished the job from Somport mountain pass in the West (from here I do not know the border well) to Vielha Val d’Aran area in the East (where the existing cartography is much better than the “CIA” one).
135 Km of border where the registered mountain peaks and passes match well.
Now I will begin to add mountain trails and everything related with.