I think there should be daily intercity between BGP - Barbil Via MDP - DHN - BKSC - MURI - TATA - CBSA.
There should be separate Train from Jogbani to Nagpur Triweekly SF Express Via PRNA - BJU - MDP - DHN - BKSC - RNC - DURG.
People from Bhagalpur can catch this train at Naugachia.