The NEC 2014 no longer permits multi-wire branch circuits that are protected by common trip (aka: 2 or 3 pole) circuit breakers or single-pole breakers connected by handle ties used  to serve emergency lighting and power circuits.

Using multi-wire circuits, emergency lighting and power could be interrupted due to ordinary line-to-ground faults or other problems where common trip circuit breakers or breakers using handle ties are used.

This restriction also applies to the three or more lighting branch circuits, supplying normal lighting, in a separate and uninterrupted area, when you are using the exception for unit equipment that normally requires it to be on same branch circuit as normal lighting.