If you have seen WAG5 Banker Pairs (or Triplets), you will know that most of those locos are very old and have come to last few (or couple of) years of their codal life. Hence, those locos are being removed from banking duties and WCAM3 will be used. WCAM2/2P have problems related to MU Operations and hence they will be used as single locos for Express Trains. As far as WAG7 Triplets are concerned, they can be used even as single loco for hauling freight trains anywhere in India (under AC Traction). Although WCAM3 (in AC Mode) can also be used in similar ways, the problem is that crew (other than CR/WR) is not trained to handle these duel mode locos. Hence, best use of them is in CR Ghat Sections for banking duties!