Those tags and others (gtfs:route_id, gtfs:trip_id, gtfs:trip_id:sample) will be used by PTNA to perform some QA on Route/Route-Master relations of OSM (Ptv2) - besides PTv2 related other QA (finding gaps, against one-way, …) . I’m currently working on GTFS/OSM comparison. This includes at the moment GTFS-trip vs OSM route, will be extended to GTFS-route vs OSM-route_master.