It seems to imply that you could take 3-phase circuit (e.g. a 3-gang 20A breaker) and run it to a triplex outlet above a cabinet; and drive three separate NEMA 5-20 outlets from the three separate phases. This could be a huge cost savings, if you could power three separate 1/3 cabinets with only a single 5-wire run (3P+N+E) back to the service panel or PDU.
If it's legal; then I wonder if all three phases (three breakers) would need to be connected and trip together as a single unit; or if you could use three separate breakers, which could be tripped separately.
I think that this is basically what happens with houses: one house might be on phase A, the next on phase B, and the next on phase C. The load of the three houses balances somewhat. If you pop the main breaker on house A, then the load on your pole may be uneven, but that doesn't mean that houses B and C need to be shut-down.
However, what works for houses isn't necessarily permitted for a 3-gang outlet box.
triplex 3-phase: brilliant or illegal?
