I think the version I read in translation had that same cover; it rings a bell. Were there also interior illustrations by the same artist? One of the details that caught my attention was the sign on the train that read DANGER: DO NOT SPIT ON THE FLOOR. At the time I could understand NO SPITTING signs, but DANGER seemed a bit over-dramatic, and as I think it was mentioned during a dream sequence, I finally decided it was a surreal exaggeration of something Emil had seen on the real train. In retrospect, I suppose the sign was probably real, and phrased that sternly because it was a warning not to spread TB germs.

I noticed when I googled Pony Hütchen that the character now has a vegan cosmetics company named for her.