I'm not too sure exactly what you mean by 'this' but I'm just making a (potentially massive) assumption about their cut off using information from previous years and I know for 2011 entry they didn't drop below 37/38 points (old system of out of 40) as they told us that on our interview days.
If you meant 'this' by how I knew about the interviews, it's because I myself (a graduate) was interviewed, and they went through the interview scoring system with us on the day and also told us they'd be using the same format (MMI) for everyone who was shortlisted for interview for 2012 entry.
Thought it'd be helpful to get advice from someone who went through the system successfully :-)