Here is a picture of their 2009 bot from CD's Media:
http://www.chiefdelphi.com/media/photos/32952
As you said it appears that they are using angled plates in addition to the spiraling. Here is another picture of the rollers:
http://www.chiefdelphi.com/media/photos/32855
We are also planning on doing something like this to our initial intake leading to our conveyor system. I hope those links help as a proof of concept. Good luck! We'll see you at 10k Lakes and hopefully at a pre-ship scrimmage.