PIKO offers the ‘Silberling’ passenger cars in a variety of liveries (e.g. DB AG, City-Bahn, Alex) for a few years now, but a matching control car was missing. PIKO then finally announced a type ‘Wittenberg’ control car (Art.No. 37635) as a 2015 new item, which is now being delivered.
Christian Fesl posted two photos of the new control car at the German ‘Gartenbahn Spur G’ forum, you can find them here: Gartenbahn Spur G – PIKO Steuerwagen