Check out the use of sections (http://ez.no/developer/ez_publish_3/documentation/customization/custom_design/sections). I think it will serve your needs pretty well. I plan to use two sections with override templates to serve up two sites that are somewhat interrelated, much like what you describe.
Then you can set up your multi-site configuration to keep content separated from the user's point of view, but still be able to grab what you need on the back-end.
Alex
Alex
[ bald_technologist on the IRC channel (irc.freenode.net): #eZpublish ]
Thanks for your response Alex. I can see how you'd use the show property to only show nodes with a certain parent node from the tutorial. But how do I use a section to show all nodes under a top node (not just the immediate children, but nodes of all depths under that top node)?