Update: The Nov 13 2012 Steam update removed the ability to play TrackMania.
Last night we were informed that Trackmania Nations Forever works with the Linux Steam beta. Turns out it does, kinda. Steam will download, install, and run Trackmania Nations Forever if WINE is detected. Without WINE installed; Steam will download Trackmania Nations Forever but fail on the install.
Will Steam for Linux have a compatibility mode for select Windows games? Hey, it might speed adoption.