Let me tell you few things
Vikramshila and Magadh express used to run as 1 unit before, all the halts of Vikramshila are from that time. Vikramshila used to run as intercity between BGP & PNBE.
Ara and Buxar were halts then as well.
Second thing, Karharia Halt was demanded by MP of that place, that was in news from the day he asked...
more... for it.
Why NCR gave halt of Sampoorna Kranti at MZP, Purushottam at CAR, rewa sf at sirathu, Mahabodhi at Bharwari?
Prayagraj ko chalao JEP se aur ye sare halts cater karo.
Ek aur chiz Magadh was of NR, It was Railway board's decision to give RSA of Magadh with HTE IPR, Because so called best zone of ir, the fastest zone of IR used to run 12402 3-5hrs late on regular basis and in return 12401 used to get late. Baith ke lakh khamiya nikal lo, jaha se tum belong karte ho waha bhi aisa hi hota hai.