Mysterious coaches

[Super]

In my uneducated guess: I just can't see a uniform color change all around the model as being due to UV rays. I would expect to see different shades of color change. The sides that face the sun for long periods of time being a different shade of change than the side that doesn't. This would really be evident in any white or light colored areas. These coaches all seem to be an even color all the way around. I long for the day we get some kind of confirmation as to what these are but until them, for me, the mystery continues.