I wonder how they define photography for private use. Many railway photographers these days share their photos on playces like Flickr, Facebook or DeviantArt, or have their own private photo sites.
Would that still be private use, or could you get into trouble with SBB over that?
Concerning the situation in Germany, I had a similar situation of my own, not actually on railway property but photographing trams in Freiburg about 5 years ago. I was approached by a security guard who claimed he was on one of my photos (I hadn't even noticed him before) and demanded I delete all my photos. When asked why, he said he didn't want people to recognize where he worked and said something about tram photographers always sharing pictures with nazis and the mafia. He sounded a bit mentally deranged to me. He called the police, actually telling them he had apprehended a shoplifer. The policemen inspected my photos and confirned that he wasn't actually on any of them.
I later wrote to the security company whose name was on his jacket but never got a response. So I guess they don't take misbehaviour by their staff very seriously.
But this is one random incident in about 30 years of photographs, so I chalked it up to an imbecilic individual.