Using a Ajni loco makes it easier for the controllers here.
Having locomotives running light between VT/Kurla/Dadar and Kalyan is difficult to manage, as the route is already very congested. Providing free slots just to move idle locs (in addition to the WCAM3s that already have to be accommodated) is quite a tedious job for the controllers considering the heavy mainline and suburban traffic on this section.
Having a loco from Ajni or some other shed, makes it easier for the controllers as the locos can be sent back to their respective...
more... sheds with regular trains, instead of having them run light, and occupy operational slots on the route.