Exactly. I dont remember it with 100% clarity so kindly correct me if I am wrong, When BOE-KIR direct line's gauge conversion was carried out, they followed two types of approach:
1. For half the section, MG line was upgraded to BG while still being operational, meaning that the existing MG line & the upcoming BG line shared same sleeper (similar to story of NG+BG between NJP & SGUJ or MG+BG between SGUJ & BORA)
2. New bridges were made for BG line, separately than MG bridges.
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That's why in this section at some places, you can trace the earthwork of old MG lines, but at other places, it is not visible.