Well, I did a little research and it seems that MTW does not offer widescreen resolutions out of the box. It seems that the most you can get on a widescreen display is the standard 4:3 resolutions plus black bars left and right. On ATI cards you probably get black bars on top and bottom too as they seem to be unable to handle fixed aspect ratio scaling.

I haven't tested this myself, but there are some insightful threads on www.widescreengamingforum.com for all those interested.

Maybe a developer or some other knowledgeable person here could confirm this?