Small Houses/Huts just outside the Train station in Berlin.

Not sure about what’s just outside the Berlin train station, but I do know that it’s common to see small hut-type structures in community gardens throughout Germany. People go to work in their gardens and then sit outside their huts drinking coffee, visiting with people who have neighboring plots and just enjoying being out of doors,

This was more of an isolated Community than what you're describing.

Many German community or allotment gardens are near train tracks and often near junctions.

I think that is what you saw.

Have a look at this article from Deutsche Welle the news organization, with a photo. Is that sort of what you saw?

http://www.dw.com/en/everything-you-need-to-know-about-german-garden-colonies/g-38857628

keim, did you mean the elevated HBF, or one of the other big stations? For example, there are two little buildings near the Tiergarten station that are actually municipal transit retail operations.

Nigel, that is exactly what i saw! Thanks!