One player doing the bass part and the other doing the melody on the same guitar isn't that unusual as a stage trick. They just each take 3 strings and go for it. It's not all that more difficult than two handed piano:
 
http://www.youtube.com/watch?v=1XsWI9EEric 
 
The impressive part of the Tico video is a section in the middle where they are fretting one part and picking the right hand of the other part. That kind of ups the difficulty, but not something I think a lay person would pick up on.  It's kind of fun to watch though.
 
CR