My initial reaction is that they are a part of a jäger battalion, probably the Ersatz company still back in Germany. I just cannot seem to make out that shoulder strap.
most of the men are wearing the 1915 Feldbluse . Would they be issued with the shako's as part Pioneer kompanie attavhed to Jager Battalion?
The officer lookes to have a very dark collar as well as the band on the Shimmermutze looks black .
mark