Upcoming BB interview from Boutique

I have coming up this week a set of interviews with an IB group at a BB, probably for an Associate position. It will be in person (no phone interview preceding this) and would like some advice on what to expect.

Some background. I currently work as an Associate for a very small (read: tiny) IB boutique firm that specializes in a niche industry segment. I have been in this position for the last two years and was my entrance into the banking world. The only other finance experience I had other than my current job was a two month internship with a small brokerage house just before I joined my current firm. So, I came into this in a non-traditional way.

I got the interview with the BB firm by cold-emailing the MD at that BB who covers this industry niche, and he then arranged for me to come in.

Just wanted to know if anyone else has had an interview in a similar situation and how I should expect to be received. On one hand, I have developed somewhat of an expertise in my coverage industry (and starting to have my own small book of CEO and corp-dev contacts). On the other hand, while in my current position I did some of the traditional Analyst/Associate tasks (pitchbooks, financial modelling) I did nowhere near what a BB Analyst/Associate does in 2 years and only for very small deals. Plus, I didn't go through an MBA, only something similar (but different), without rigorous education in financial analysis

Thanks for any advice. I've never been interviewed for a BB before. Could be helpful multiple times because a few MDs at some of the other BBs seem interested in bringing me in to interview too...