Refer to this post by Yogesh Sir ( He is not on IRI anymore I guess). He was a local RF at Pune, familiar with all the operations at the station.
/blog/post/1600882Apparently, due to severe congestion at Pune station, the authorities had said 'No' to loco changes for any trains at Pune other than a few trains which had already been running for a long time and under-going loco change at Pune for a long time ( Like DR-MS, Jayanti Janata, MAS-CSTM mail etc).