To be sure it's understood, I'll try to clarify if I can. There is a straight line run of conduit feeding a lighting circuit from a panel to jbox A, jboxB and the switch for the lights. The switch leg comes from the switch in mc and feeds a row of lights. At the end of the row it loops over and feeds the next row and at the other end of the row goes to B. For convenience sake, the switch leg goes through the conduit that carries to A. From A it feeds mc to the last row of lights.
I say that you need two neutrals in the conduit from A to B to keep it seperate even though it is the same neutral.
