this is the way I see it, the / and the will need replacements for their r46s, and if they give new techs to the , those 68s would get transferred to CIY to replace them.
However there wont be enough of them to cover all 3 lines, hence where the r68/68a trains would be enough to fully cover the rest and then some and since its based out of CIY they can use those cars as spares for broadway service if need be