Interesting read. Reading articles like this makes me wish the sources to some of those older RTSes (Starcraft, Warcraft, Age of Empires) were available to look at - I'm sure there'd be some interesting stuff in there.
ETA: Just remembered. They open source 7 Kingdoms a few years back so you can find out what the code from a commercial RTS looks like. http://www.7kfans.com/wiki/index.php/Download