Sir,
Seems u havnt gone thru the train's route!!!!
It doesnt enroute MGS, else diverts through Sivan-Bhatni-GKP Route!!!!
Again, to divert train via Mau, means extra running time & its only possible if any regular train will strt from GKP towards NJP which can run via GKP-BSB-NJP or, GKP-MAU-BALLIA-NJP.