Those Austrian Sidecars used to harry retreating Italians in 1917, research so far indicates that Puch were major suppliers of motorcycles to the Austrian Army during The Great War. (However, there was a Hungarian manufacturer called Meray, founded sometime between 1919 and 1921.) The light machine guns that they were equipped with was most likely the double-barrelled Italian 9mm SMG Viller Perosa. (It was copied and used by the Austro-Hungarian Army.) They could also have been German NSU bikes and sidecars. In 1915 the German Army acquired a number of NSU motorcycle combinations with a rearward firing MG in the side car. It's possible that the KuK Army aquired some as well.