It has always been my understanding that NEC required abandoned wiring to be removed. But as I look through the code, the only reference is in article 645. 645.5(G) states:
(G) Abandoned Supply Circuits and Interconnecting Cables. The accessible portion of abandoned supply circuits and interconnecting cables shall be removed unless contained in a raceway.
Since this article is entitled "Information Technology Equipment", does this apply to any abandoned wiring? i.e panelboards, switchboards and removed equipment?