I would think that you have answered your own question. If they are UL listed and they are used within the limitations of that listing I cannot see how anyone could turn you down on them.
Of course I have had a fire pump controller that was UL listed as Suitable for use as Service Equipment red tagged because the inspector wanted a fused disconnect ahead of it. The contractor I was working for obliged him because his order made it an extra for us. If he had just written it up for the lack of a Grounding Electrode system and their failure to pull a grounded conductor from the wye connected transformer to the controller I'd have been silently cheering him on but I digress.
My point is that just because we haven't seen it done that way before does not mean it is bad practice let alone a code violation. Remember that the code itself says
[90.1 Purpose.
(C) Intention. This Code is not intended as a design specification or an instruction manual for untrained persons.] Copyright 2002 National Fire Protection Association.
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Tom H
