The problem with using the dedicated space and working space requirments are that its not a switchboard, panelboard, or MCC. However, I think the 1st sentence of 110.26 would make this a violation (although that sentence is wide open to interpertation.)
I would also call it a violation based on 404.8 - switches have to be readily accessible.
I also doubt the enclosure was meant for wall mounting - it was probably intended to have a floor under it. I would expect the frame to eventually bend, and cause all kinds of havoc.
Finally, I would also have no problem calling it a violation under 110.3.
Did I mention I would call it a violation? IMO, ATS's need to be readily accessible, both for the on site maintenance people, and the ATS service people.