I think IR won't built any dedicated shed for P5/7 in ECoR & SER region, rather they will upgrade the existing sheds to home P5/7. Moreover in my
#railwayengineering series you will find a dedicated blog on TATA ELS of SER where you will find that TATA ELS is completely equipped with 3-Phase Loco repair and maintenance facility so if WAP-7 is provided to TATA they can cater to the service of SER and ECOR very easily.(/blog/post/1551102)