Interviews are not conducted at open houses at any schools with which I'm familiar. Officially I don't think any school will tell you that attending open house will help your chances of admission. I suppose it's possible that if you spoke with and made an impression upon someone from the admissions committee that you might be remembered and that it might help (assuming it was a positive impression.)
But: it isn't always the case that the faculty (and students) who are around at open house are the same people who are on the committee, or that you'll get a chance to speak at length with many of them. Fall open houses tend to be fairly crowded (whereas the ones in the spring for admitted students are sometimes a much smaller thing and better for actually getting a good feel for the program and speaking at length with people. At that point they're actually familiar with you/your work to some degree too.}
I remember going to the open house for my top-choice school, hoping in particular to meet and talk with a particular faculty member. But everytime I spotted this person he was surrounded by other prospective students, 3 people deep.
I would go to open houses with the intention of seeing the facilities, sitting in on a studio crit and/or a lecture (most schools schedule their best lecture of the semester for the evening of their open house), and getting a general overview of the program, the mood, the place, etc. But I wouldn't base my decision to go on thinking it would help my chances - because I think that's a a pretty small chance.