Bob If thats True where in the N.E.C. does it deal with parellel conductors over 600 volts .???? There are Several references to over 600 volts in Art. 310. & 300.3 B(1) referes you to 392.8d Parallel conductors in tray, which is deals with over 600 volts in that section(Tray).
"Scope.All Wiring Installations. This article covers wiring methods for all wiring installations unless modified by other articles." Since the over 600V sections do not modify the rules for paralleling I would say that they apply.