The story
The StEG was founded on 17 October 1854 primarily with French capital and on 1 January 1855 bought the Northern State Railway and the Austrian Southeastern Railway from the Austrian state, hence the unusual name of the new company. By procuring the Vienna–Raab railway on 13 February 1855 and the Brünn-Rossitz railway on 1 January 1879 and building new lines the StEG network within the Austrian part of the empire had grown by 1890 to around 1,350 km. In addition, there were 1,500 km of railway in Hungary.
On 15 October 1909, the StEG was nationalised and with it became a part of the Imperial Royal Austrian State Railways or kkStB. The routes on Hungarian territory had already been transferred to the Hungarian State Railway in 1891. That included the Bruck–Nickelsdorf and Marchegg–border sections, which did not come into the Federal Railways of Austria's (BBÖ) possession until 1920.
From Wikipedia’s article on Imperial Royal Privileged Austrian State Railway Company, shared under CC BY-SA 4.0.3