I see that the definition of multiwire branch circuits requires the non-grounded conductors to have voltage between them. Having two single-phase 'line to neutral to line circuits' sharing an oversized neutral would NOT be considered a multiwire branch circuit.
110.8 says that only wiring methods recognized as suitable are included in the Code. By inference, other wiring methods not recognized by the Code must then be questionable, and therefore the inspector can freely reject them.
Anyway, back to curiosity prompted by Rob's original question, I too would like to know why the Code allows such a freak multi-multiwire feeder circuit. What would be a typical installation for such a scheme?
