Shocking, but NEC 705.12(B) and (B)(2)(3) are not consistent. 
Up in (B) it says:(B) Load Side. The output of an interconnected electric
power source shall be permitted to be connected to the load
side of the service disconnecting means of the other source(s)
at any distribution equipment on the premises. Where distribution
equipment, including switchgear, switchboards, or panelboards,
is fed simultaneously by a primary source(s) of
electricity and one or more other power source(s), and where
this distribution equipment is capable of supplying multiple
branch circuits or feeders, or both, the interconnecting provisions
for other power sources shall comply with 705.12(B)(1)
through (B)(5).
It definitely includes switchgear, switchboards, and panelboards here and specifies that (B)(1) through (B)(5) applies to them all. But then you get down to (B)(2)(3) and it says:
(B)(2)(3) Busbars. One of the methods that follows shall be used to
determine the ratings of busbars in panelboards.
Inconsistent I know, but I think it's easy to argue that since (B) says it all applies to switchboards and switchgear even though (B)(2)(3) does not write all three out that (B)(2)(3) applies to switchboards and switchgear. But is there is an AHJ that just reads (B)(2)(3) and not (B) or ignores the connection? Anything is possible. Can someone use this to say they can back feed a switchboard up to the bus rating? They can try but I don't buy it. The same theoretical limitations apply to all three.
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