The signs were discovered in 2012, and a newspaper article (in French) tells the story of that discovery. Renovating the facade, workers removed a wooden structure placed there in the 1930s and uncovered these remarkably well-preserved signs. Cartoonist Jul alerted the local authorities, and work was stopped. Over a century after the Ripolin advert was created by cartoonist and poster artist Emile Vavasseur, and the Benedictine advert by Defoly, the adverts have been designated a Monument Historique (listed, in effect) for their historical and artistic interest. Tantalisingly, the listing text refers to a third sign which could not be preserved.
Funds were being sought for restoration (a sometimes controversial option in Britain), which would cost several hundred thousand euros. In the meantime, the painting is covered by clear sheeting. The covering may not be ideal - it rather obscures the signs - but it has saved them from graffiti as well as the weather. A little messing around in Photoshop allows us to see the painted images more clearly.
As usual, click the images to enlarge them.