Did some checking around and its not so simple but possible. Might require a specific build of wine. You also have to point it to some directx dlls or some such. A quick google shows a lot of pages that have information on how to do it. Punkbuster might be an issue since the XI servers use it. Truthfully, you might be better off doing a dual boot and having one small Windows partition to use only for games. In the long run much less of a headache.
By server, I mean if you want to run your own cod4 server for everyone to play on. You run the server. Install the maps. The mods. But, it is not a listen server like in MW2/3/others. So it is not a client for you to play. Just a command line window. Many game server providers use it tho windows is better to avoid certain Linux limitations regarding bigger or more complex maps. For this kind of thing you dont need wine.