Having tested with Crossover Game 9.2 for Mac I can say that the only workaround needed to get the Steam Version of the game "running" is to change the following option in ~/Documents/BFBC2/settings.ini:
From: DxVersion=auto
To: DxVersion=9
This will get the game to run and work as far as the menus are concerned. The need to do this is currently due to a bug that is being tracked in Wine-dev.
The only problem is that there is a d3d rendering issue in Wine 1.2 which was fixed in Wine-dev 1.3.9. The bug is 22617 and is listed here:
http://bugs.winehq.org/show_bug.cgi?id=22617
I was able to use WineSkin with Wine 1.3.9 to play the game online and in single-player mode. In single-player mode the only other problem is that the cut scenes have a timing issue and play too quickly(in a few seconds rather than a few minutes).
I think we are one bug fix (one that is already fixed in Wine-dev) from having the game being Bronze quality.