A interview is a good sign, as it demonstrates that they are interested in you. It also represents a very important step for you, as it exhibits a strong influence over whether you are accepted.
As for preparation, Tulane can ask all sorts of questions. Obviously, know why you are applying to Tulane, why now, why not an MBA, and so forth. Know about the city (I'm actually from New Orleans, by the way) and some of the faculty members.
Also, read the Financial Times, the Wall Street Journal, and the Economist
daily in order to prepare you for any possible questions from current affairs. They might also ask technical questions, but your educational background should guide you through that.
And, of course, know about your company and its history. Be able to fully describe your duties.