Well if you use the legal app store version of Rome total war you get a launcher in which you can type in things like "-mod:EB" which activates EB once you've placed it onto the RTW data.dmg.
I don't want to rush to conclusions but it seems like the copy you use is not legally obtained. I hope I am wrong. Or perhaps OS Lion has altered the launcher for some very odd reason. I am still on 10.6.8 OS X.