I am not sure, someone was looking for ways to manage several blogs off of one WP install. Anyhow there is this new plugin that popped up that some of you might want to consider.
Supposedly it manages themes and plugins plus core files from one location. Allows for multiple admins.
According to the Plug In page, upgrade or change a theme would effect all the blogs under it’s control. The way it looks, from the warning about admins for the other blogs, is that any change at any blog to the plugin / theme would be for all. So you could do it from any of the blogs.
I have not used this plugin, but I have been using a similiar one since November on some 2.3 blogs. Which has been working great obviously. Makes it easy to update plugins and use them all off one install location.