I've passed here from Hameau de Stoqueue to Niaster and on both sides there are signposts indicating this domain is private (seems to be confirmed also by http://biodiversite.wallonie.be/fr/1434-carrieres-de-niaster.html?IDC=1881&IDD=251661050). See Changeset #140029580 . I'm not sure to which of the (other) roads the restrictions apply though, so if you have local knowledge, feel free to refine!