(b) Conductors of the Same Circuit. All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, trench, CABLE, or cord, unless otherwise permitted in accordance with (1) through (4). [not applicable here]
i've understood this to mean that you can't run SE cable with 2 ugc's and 1 gc from a service disconnect panel to a sub-panel, and then run a separate 4awg cu egc [you know, outside the sheath].
i saw this in a new house and it made me question what i thought i knew. -C-