Hi Nick,
The motor is behind the seatpost with a belt drive to the rear "differential" hub.
Here are a few links that explain it:
http://www.evworld.com/news.cfm?newsid=14643
http://www.velocity.ch/
http://swizzbee.com/index.htm
http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US5242335&F=0
http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=US6286616&F=0