Looks like the experiment has been stopped now and KK is back to diesel link between DD-SBC. CR has cited some issues that were observed during the trial.
Since KK is already a 25 coach ICF rake, it is close to the hauling capacity of a single WDP4B/D. With the dead weight of the P7 (which itself is a rather heavy loco at 123 tons) the rake is now equivalent to a 28 coach ICF rake, and is pretty much at the limit of where a single EMD can maintain the schedule. In addition, it will also increase the fuel consumption and the general maintenance requirements for the EMD. But they have cited that they will continue...
more... looking into this experiment more.
May SCR can take over the loco link again and provide GTL twins between GTL and DD. Earlier when GTL was providing the link, the Down KK used to have a loco change at GTL where a new set of twins were provided. Something similar can be done now with an E-loco taking over instead.
I would still prefer it to depart from SBC with ALCO twins though. :)