According to what was said last year, TS09:EE will work as a kind of 'patch' (much like a service pack) if you have TS09:WBE installed. It will install the existing content into WBE, and put in all the code updatesm, and basically act as a patch. They will become one game. Or at least that is what Tony explained to us...
EE on it's own is supposed to be able to download and run additional content, including new routes, and so on...
Zec