Andre,
You may want to search Delaware & Hudson structures. The president from the late 40's to the 60's, I believe, was big on using concrete structures to reduce maintenance. Bridges and such, but I seem to think it grew into replacing small wooden service buildings. I believe the shanty actually came from them as they began using tracks (old PRR) in the area of where the shanty prototype photos were located.
I found that reference when searching for details about the concrete switchman's shanty.
