Re: Two Panels,One Ground
I agree with Bennie on other than multiwire circuits.
The grounding conductors with a multiwire circuit is not addressed in 210.4(A) which in part states "- - -. All conductors shall originate from the same panelboard."
Whereas 300.3(B) requires all conductors of a Circuit to be in the group including the grounding conductor.
I am not sure if there would be a problem with multiwire ciruits of two different panelboards sharing the same grounding conductor provided the grounding conductor is sized per 250.122 for the OCPD of the highest amperage Branch Circuit.