The role of so called "Tamil Lobby" is only responsible for this.
The Mas-plni exp which is now running upto poy is not extended till pgt only bcz they dont want their train to go out of their state;they are waiting for ptj-poy route work to finish and then extend it to CBE...Also if trains starts via pgtn-poy route,mainy train might be introduced via konkan to rmm or mdu via this route so they are afraid that CBE would be neglected .