Well, I watched it over for a second time just now. And I pretty much don't have much to say It is exactly what I was looking for. I think the methodology you're using is just right.
Trying to think about the level of stress this would put on the server (not exactly easy right now, I have a bit of a cold, so I'm thinking through lots of drugs at the moment, heh). It seems to me that we're good. For every wall, the server would have to send a position (and possibly an angle) along with an identifier to give the exact type of wall, perhaps some color data (that would allow people to customize the color of thier walls), and a frame index.
So six floats, an int, three bytes, and another byte (I will presume there will be less than 255 total frames for any given wall, but if we end up with more, we could always change it to two bytes).
All of this would have to be sent for every client that walks into the neighborhood (with the landblock data I presume).
Seems like it should work. Even if there was a lot of people coming into a large town, all that data would only go out once per person. I suppose it could be a lot, but not much more than if we were just sending static building data.