There are certainly ways to recognise the newcomers (legal or illegal) in Germany when you ride the trains based on my summer trip this year and that of last year. Anyone who can't spot that out does not know Germany. It depends on which type of train it is, sometimes where the train is going, ie the area, etc, or when the train is. I've seen stowaways (women and kids) taken off the train escorted by the Bavarian Polizei. That was in Rosenheim in 2016.
These two latest trips I took a total of 4 night trains...never saw any migrant types on the platforms waiting for the EN night day, or coming off the train at the train's terminus. On the ICE and IC trains, I never saw any migrant types or heard them on board (easy to discern) or waiting for the ICE or IC on the platforms.
On the RB trains is where you would see them, be it in Schleswig-Holstein, en route to Kiel or Neumünster, the Hamburg to Bremen route, the lower Rhine area near Düsseldorf, such as Wesel, Mönchengladbach, en route to Venlo (Holland), in Westfalen and the . Hannover area...ie, you ride the Regional Bahn to get out to the towns next an urban center, you'll surely run into them taking that RB train. . Numerous routes were only standing room because the train was so crowded. In eastern Germany fewer chances of encountering them, not the places I went to...Jena, Neustrelitz. At Halle Hbf they were there just milling around.
This summer's trip I saw no one escorted off the train, contrary to last year when on one occasion when crossing the border back into Germany from Austria, I heard the DB controller announce that everyone had to get their tickets, passports, and visas out to be checked. at which time I got my rail Pass out along with passport.