Either that, or a 277/480V panelboard re-purposed for the system. I can't think of a specific application where you would do this. However, just as a theoretical question, if you do satisfy all voltage requirements of all breakers, is possible/permissible to use the high leg for a 208V single phase-to-neutral load?
You would theoretically be using the high leg and a neutral from a 240v 3ph service for a 208v single phase load, and no, hopefully not in my lifetime anyway.
JAP>