You should be able to transfer them over. The file types and formatting of the presets are the same between Mac and Windows and shouldn't cause any issues. I've tried replacing the 1.1 Mac Presets folder with the 1.1 Windows Presets folder and it works just fine. You can then even use SoftStep Converter and Librarian to transfer them over to the 1.2 Mac version.
Since the Mac version uses SoftStep Share as its output device in Hosted mode and Windows uses something else (generally MIDI Yoke), there may be some small editing you'll need to do in the "device/route" fields. Other than that you shouldn't run into any problems.
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