Are the placements of BIT extension campuses centralised at BIT Mesra?

To some extent, yes, the placements of BIT extension campuses centralized at BIT Mesra. BIT extension campus students are permitted to sit only for a limited number of companies; recruiters such as Cognizant, TCS, Infosys, to name a few. Other big firms like Goldman Sachs, Amazon, Caterpillar tend to interview only the top 5 students (top CGPA holders) from the concerned branch in each campus are allowed.

Apart from this, extension centers are free to invite recruiting companies to their respective campuses for placement drives. For instance, in the past, MU Sigma and Tata Motors conducted a pooled placement for BIT Patna, IIT Patna, NIT Patna. 

If you are someone who is successful in attaining a 9 pointer throughout your course duration, you have made impressive and exciting projects and conducted research for the same, you certainly stand a good enough chance to be equivalent to all other students at Mesra when it comes to your placement.