Let's not try to split hairs here.
The primary OSHA statute is Part 1910 of the "Code of Federal Regulations." Subpart S, Appendix A, is a list of standards theat "may be useful" in complying with the 1910 requirements.
NFPA 70-E is but on of many standards on this list.
Now, what that means to me is that if your practice is different from what 70-E calls for, you ought to be prepared to litigate for years, and convince a dozen complete strangers, that your opinion is better than what that nice "government expert" offers.
I would say that you ignore NFPA 70-E at your own peril.
As for the "consensus standard" issue, I think that particular canard was put to rest by the Veeck case. Once a standard is adopted as law, law it is ... no matter how it was written. On the "down" side, you get to obey it. On the "plus" side, the "author" can kiss his copyright priveledges good-bye.
70-E is certainly referred to in the OSHA Statute. If I were asked to pass judgement on whether this made it 'adopted by reference,' I would say "Yes." You can be sure that every standards group would argue for a more definitive means of "adoption."
