Somewhere, I have an original picture of those box-cars that was taken by a friend of mine just a few (10) years ago.
The first though I had when Q dropped, but , as the other anon said, had not seen the acronym.
This was not the first time. In the '90s an army reserve Captain told me he saw a fenced compound that was full of these on Ft. Richardson in AK.
I'll bet that a lot of these are not crashes etc. at all but fake stories to cover-up suicides/187s or other disappearances.