electric railcars gotthard line lötschberg line SBB Re 4/4II SBB Re 4/4I SBB Ae 4/7 mainline buchs-st.gallen olten SBB Re 6/6 SBB Ae 6/6 RAeBD railcar brig along lac lemon zürich hbf mainline bern - brig trolleys basel trolleys bern trolleys zurich