I see that the Illustrator Scripting reference document for CC 2014  has references to FXG, FXGSaveOptions, etc. I thought I would give it a try to see if I can save a document to FXG. Here is what I am trying:
var myDocument = app.documents; var myTextFrame = myDocument.textFrames.add(); myTextFrame.position = [200,200]; myTextFrame.contents = "Hello World!" var newFile = new File("c:/temp/fxgfile"); var fxgSaveOptions = new FXGSaveOptions(); myDocument.save(newFile,fxgSaveOptions);
This causes the file to get saved as fxgfile.ai and not fxgfile.fxg that I was looking for.
I've attempted to modify other script samples from C:\Program Files\Adobe\Adobe Illustrator CC 2014\Presets\en_US\Scripts and use FXGSaveOptions but it outputs a 0 byte FXG file :/
I'd guess that the FXG options are remnants of when there was built-in FXG support but no longer do anything.