@Lack of finding names an idea popped in my head about this which is sole speculation but I am sure @Carnage Evoker would love it. What if the four classic maps were originally intended to be busstops in Tranzit?
We have Nacht already. We also have zombies with mysterious badges of "Hanford Sanatorium" on them, which perfectly fits with a structure similar to Verrückt being somewhere out there. Der Riese, also referred to as "factory", would easily fit as one of the nuclear factories that were present at the Hanford Site. In the pre-Alpha concept art you posted earlier, we even see factories as an intended area in Tranzit.
Shi no Numa would be a bit more tough to place, but it would actually fit quite well with the wooden barns, fences and other structures found in Farm. The area itself even seems to be covered in a green fog as opposed to the red colour encountered in the rest of the map, quite fitting with Shi no Numa.
Now, the maps may not have entirely been put in Tranzit. Think of it more like Tranzit's Nacht, which is partly accesible and a bit changed when compared with the original map.