In my app (cordova - android/ios) i integrated ga and it work fine for now. What i have problems with is to track the targets inside a world. I think the ga is not loaded in the world. I found no way to do that (also not to output to js console from inside world).
In the attachment is my WikitudeLoader.js and world files.
I recommend you to use latest GoogleAnalytics JS library and track actions directly in your AR experience's code (using ga('send', ...) ). That way you can use same tracking on all clients. Please note that, by default google analytics uses the same protocol as used for loading the html file it sits in. Ensure to set https protocol when loading ga-assets.