The old departement numbers were 67 + 68 and the new one is 6AE
I think they actually remain 67 and 68 - the departments weren't abolished, merely their councils were and the administrative functions given to this new body (along with some devolved from the region). I think the code, as we would see it, for the new body is actually 6A, with the E standing for 'Collectivité européenne', but I'm not sure. In 2019, Paris' commune council and department council merged into a single commune council and INSEE gave it the new authority the code 75C (C for Commune) - that hasn't translated to number plates and all that, AFAICS. Similarly some of the DOMs are governed by Regional councils after department and region merged into one council and so are officially 97xR (R for region).
We can always drop the E later, if I turn out to be right.
Except of N159 if I got the source right "the RN159 being granted, it will remain RN159".
Not the best translation, but yes, the N159 remains untouched. AFAICS it's roughly* "NB: RN159 is a
concession, it remains RN159 - the Autoroutes, concessions or not, do not get renumbered."
Basically, because it's a road that isn't run by the State, but by a semi-private company on the state's behalf (it's a tolled tunnel), it didn't move to Alsace's control, and so they have no authority to renumber it. The tolled bits of A36 and A4 ditto. They aren't renumbering the free autoroutes that they have direct control over.
*taken from the text of the map, based on the little French I have and my knowledge of French roads.
