Initial contact was with the HR recruiter on campus at b-school. However, I was rejected by the recruiter. I still ended up on the interview list because my university had a bidding system which enabled rejected candidates to interview.
All my interactions with the senior managers were great. All were smart, personable, friendly and genuinely interested in meeting the candidates. Sadly, I found out after joining the firm, that they were an exception to the rule and had self-selected as volunteers to interview.
The interviews themselves were fairly straightforward - about my work experience, leadership style, examples of success/failure etc.
A year later I had the opportunity to act as the campus representative and was able to observe the initial HR "selection process" first hand. The process was very random - I overheard some HR person commenting on how "cute" she thought the candidate was.