I have managed to get Train Simulator 2013 working on my iMac as follows.
Download and install the latest version of XQuartz.
Download Wineskin 2.5.8 and engine WS8Wine1.5.0.
Create a new blank wrapper.
Install .NET 4.0, vcrun2010, physx, d3dx9_43 and Steam using Winetricks. It is probably best to install them one at a time and install Steam last. Steam should then automatically run.
I had to force use of system installed XQuartz in the Wineskin options, it may not be needed on some systems.
I installed the Mac version of Steam and downloaded TS 2013 that way as the Windows version would not display my PayPal login page, but it has worked in the past for me using other payment methods. There are various on line vendors who sell TS 2013 if you don't want to purchase from Steam, but Steam has to be installed to play the game.
Install Train Simulator 2013 in Steam, ensure the Windows EXE is set to '/Program Files/Steam/Steam.exe' in Wineskin. Quit Steam and Wineskin.
CTRL click on the newly created wrapper icon. Select 'Show package contents' and navigate to 'drive_c:\Program files\Steam\steamapps\commom\railworks' and rename installscript.vdf to old_installscript.vdf. I am not sure if this makes a difference but it stops Steam installing DirectX, .NET 4.0 etc. that have already been installed by Winetricks. The Winetricks versions have various fixes built into them.
Double click on the wrapper icon to run the Steam application and start Train Simulator 2013. In the graphics options I had to turn on full screen (windowed causes a crash) and turn off TSX otherwise the in game display was black except the 'head up display'. It does mean no fancy lighting effects.
It seems to run at least as well as Railworks 2, but with slightly improved graphics. Needless to say cranking up the settings high slows things to a crawl!
I use the following settings
Custom master setting
Texture filtering Anisotropic X2
Scenery high detail
Scenery distance 8
View distance high detail
Procedural flora off
Adaptive bloom off
depth of field off
I have since found that Wine engine WS9Wine1.5.16AMDSpeedHack and setting the Windows version to Windows 7 in the Wineskin config utility works better with my system.
The sound does crackle sometimes, I have not found a fix as yet. You need to wait until some of the installed routes show on the collections screen before going to the main menu, as otherwise it sometimes crashes.
My system is an iMac mid 2011 2.5GHz AMD 6750 512MB graphics using OSX 10.82. I can't promise it will work on other Macs.
I hope this makes sense and is of some use. I probably have not posted it in the correct place either, but it is my first post.