Key KH doesn't exist in Austria. Values RR and 250 appear in the ref value of pipeline markers (taginfo). pipeline=marker is deprecated BTW.

According to https://de.wikipedia.org/wiki/Hinweisschilder_zu_Straßeneinbauten KH could mean "Kugelhahn" (ball valve) and RR "Riechrohr" (smell pipe), both for domestic gas.