Ostösterreich is the Austrian name of East Austria region AT1. It corresponds with the NUTS-1 https://ec.europa.eu/eurostat/web/nuts/overview region of East Austrian states of Vienna, Lower Austria, and Burgenland. Currently, there is a transportation association for this region called Verkehrsverbund Ost-Region.https://www.vor.at
Sources Hierarchical list of the Nomenclature of territorial units for statistics - NUTS and the Statistical regions of Europe A map of Austria showing AT1, AT2, AT3 areas German language wiki of Ostösterreich
References