For your information , All zones wont be immediately trained in WAP 7 , Earlier SCR was providing WAP 7 because SR did not have , Even SWR provided WDP 4. Once RPM got WAP 7 , SCR stopped the link , Once GOC got WDP 4B , KJM stopped the link. First NR got trained in WAP 7 and it went so on, SER and ECoR are not trained in WAP 7. SCR and SR are huge zones , Look at the number of divisions it has , COmpare it with ECR, ECoR. You ll find SR and SCR are biggest. So its justified to have more WAP 7.