Nathan1986:
I'm in the same position as you (not assessed on the same day, but in the same week).
I don't think my referees have been contacted either. I wanted to change my referees, as I originally put down the boss from my previous job whom I haven't seen for about four years, so I emailed them to change it (as we were told to do) but never got a confirmation reply.
Anyway, I got the impression that our referees will only be contacted either for a fairly simple verification that we didn't completely make up all the stuff in our resume (e.g. "does Nathan really work for you as a lion tamer?") *or* if there was something in the assessment day which caused them concern but they were otherwise interested in taking us (e.g. "can you tell me about how Nathan is at working together in a team?"). So I guess not having our referees contacted yet can be either good or bad news.
Or no news. I would imagine that they would have waited until they interviewed everyone last week, analysed us late last week, and be ringing our referees this week with a view to giving us an offer late next week.
I think even if we got an offer we couldn't start till next year anyway (which would be great by me). So I guess it's just wait and see, just like the last six months.
Good luck with it.