text: Actually, I think railway=disused is the most appropriate tag at the moment. The most comparable railway I can think of is the Petite Centure de Paris ( https://www.openstreetmap.org/relation/1536589 ), which has had a few trains for maintenance during the last few years, and is officially still part of the railway network, but "not exploited" (a few parts are officially still exploited for freight, but not in reality), see https://www.sncf-reseau.com/fr/carte/carte-interactive-reseau-ferre-francais-0 . OSM marks it as disused.