BCG is a fantastic Firm, and its selection process is one of the most professional. I have only good things to say about their US team.
The Indian office (esp. Delhi), however, is another story altogether. They are a right mess.
Lateral recruitment and career progression are not aligned with US or Europe, and seem patently illogical and unfortunate.
The recruitment process is fairly standard - with 2 rounds of interviews. Each round consists of 2-3 interviews. Each interview is supposed to be composed of a case and a behavioral part.
Unfortunately, the Delhi-based interviewing consultants evidently lack a key skill - listening. And irrespective of how many interviews they might have conducted, they seem particularly poorly equipped to manage case interviews. In fact, in one case, (based on the feedback later provided to me) the interviewer actually expected me to do the exact opposite of what one is supposed to do in solving a case.
To top it all, they seem pretty cavalier and unprofessional as far as the process and logistics go.