autoblog, sitewide tags, tag-feed oh my!

trying to find a way to aggregate all posts marked with the same category across our wpmu install - I thought a combination of autoblog and tag-feed could do this where the tag feed url is used as the feed url for autoblog.

While this worked if I used a feed from somewhere outside my domain - any feed from inside the domain would not work even when following the tips on the autoblog post and it looks to be unresolved at the moment. Once that works, the next step would be using the tag feed url - but without a standard domain feed working this didn't work either.

Is there another way of making this happen? tried wp-o-matic but would have to install on each blog - we'd like students to publish to their own blog but aggregate their work into a different blog depending on the topic or subject of their work.

thanks

cmb