Hello TML,
There are currently only two bus games for the macOS, which are Bus Driver and Bus Simulator 16.
You have already published so many of them like City Bus Simulator 2010, City Bus Simulator Munich, Bus Simulator 2012, Bus & Cable Car Simulator, and last but not certainly not least: 
Fernbus Coach Simulator. Now, since you upgraded to the Unreal 4 Engine, that means much better graphics and much more things in general. I know that the Unreal engine can export for Mac.
And I also know that you'd be missing out on so many customers (like me) if you only offer a Windows version.
Now, I don't know what you'd have to do that your game would support Mac, but please, I just know that you'd be getting much more customers if you'd also offer a Mac version.
Best Regards,
Ikarus280
