A primitive, but easy, way to achieve this is to use WordPress multi-site.
You can then use identical themes and use wp-to-twitter for each WP site to link to the different twitter accounts.
I’m planning to this, but have a slightly different theme on each section – different header and probably slightly different colours.
I know that there are technical ways to do this, but this is a very simple way of doing it.
The multi-sites will all appear linked as either directories or subdomains.
