Yes, it uses Wine. It would be incredibly stupid of them not to use Wine. Converting Windows APIs to Linux APIs is a very tedious and difficult process. Wine has been in development for 8 years with the goal of doing that, and even after all that time Wine still isn't past the alpha stage. That should give you an idea of the massive amount of work Wine programmers are putting into this. Seriously, the source code to Wine is mind-boggling complex.

Wine has come a long way since the Windows 3.1 days. It can emulate many programs with relative ease and quickness, and can even emulate many retail games such as Half-Life and Soldier of Fortune with pratically no crashes or bugs.