At the level of the secondary side of the transformers, we have stories of plumbers getting shocked cutting pipes, because the metal water distribution network was causing a very good parallel path between separate structures sharing the same transformer. My guess is that if the NEC could eliminate this risk, it would...but multiple buildings sharing the same transformer secondary are the domain of the POCO, not the NEC.
That is fascinating. I hadn't even considered thinking of that. I don't have much to add to this thread other than "thanks" for making this much easier to understand than reading it in a book.
--Ron
