Can't answer the question (a good one, by the way), but it brings up
another, even more interesting, question in my mind: assuming it is legal
(I'd suspect it is), what about insulation for the joint? Is electrician's
tape sufficient?


Don't see why not, tape is used on high voltage splices and you see a lot of
it in old houses too. BTW, the best high voltage splices are done with lead
(solder) - its a dying art form much like using lead on auto body repair.