How to create multi site page inheritance?

I am looking at setting up an MS wordpress install. I think that will suit my needs the best. Basically, I have a client who has a business in Town X, but wants to branch out to Town Y. They have XYZcompany.com and want to setup XYZcompany.com/townx & xyzcompany.com/towny. This seems like a great fit for the new WP 3.0.

Sorry for so much back story, but there will also be the main xyzcompany.com site and all the non-city based content. Is it possible to create a page inheritance where the site for town X inherits the content for a page from the main site? Say for example an About page, the text would all be the same but in the Town X page there would be the addition of the town name.

My thought is to create duplicate theme’s with minor changes in the code to reflect city info. For instance, (and I know this is basic);
<div>New York <?php the_loop ?></div>. I know I am dumbing it down, but would that work?

I am not looking for someone to completely answer the question. Unless there is a simple answer, but I am trying to learn how this MS stuff works. Thanks