Yes, I was surprised too. I did make an effort to include anything remotely relevant on my CV, e.g. I taught undergraduate students one-on-one for a while (not TEFL though), my degree included languages etc. But I suspect that it was my university and degree class that stood out - I can't really think of why else they decided to interview me.
The interview was actually yesterday, and for the benefit of others, it was not too daunting. The written test before the interview itself was a choice of 3 essay questions and I had 20 minutes to answer one of them. The interview focused on teaching methods and I would recommend reading about the HK school system and curriculum, and if you haven't taught primary school children before (as I haven't), you will need to research teaching methods for them - these are not covered by the CELTA. I read some books on general primary school teaching and one on teaching English to young learners, and I talked to some primary school teacher friends. This isn't a substitute for experience but it's the best I could do!
I'm not really expecting to get onto the scheme (although if I do... great!) and certainly not expecting to get a PNET job this year (although if I do... great again!). My current plan is to get experience in Hong Kong, probably in a kindergarten (as tutorial college experience doesn't count in the eyes of EDB) and then reapply next year.