I am not. To the best of my knowledge, all WDM4 locos belonged to NR and were homed at only one shed in IR, at MGS. The locos were different from the ALCOs and IR did not have technology transfer agreement for them. So all spares, maintenance personnel etc were supported by GM (the manufacturers of the loco) and they were never homed at other sheds because of this.
Particularly the Howrah Rajdhani was NEVER hauled by a HWH or BWN WDM4. As long as the HWH Raj was running with a WDM4 link, the link was based out of MGS shed only. By the 80's, the HWH Raj started running with WAP1 links full time.