data/plugins/StationSwitcherPlugin.py needs to be ported too. In the last line is print "" and instead of gtkgi.repository should be used.
Other than that it seems to work (at least partly).When clicking on anything, it takes quite long time till radiotray responses and acts on the clicking... On second startup gtk3 is crashing over here, so it might be a gtk3 issue... I have here gtk3-3.10.4-1.fc20.x86_64.
In the background I was also porting to GTK3 and Gstreamer 1.0, but not to python 3. It seems to be working, but there could be some issues still, I haven't tested it thoroughly.
Now, it's going to be interesting trying to merge this pull request with my version. Some things are probably equal, others aren't. I'm going to push my version first and see how this merges with it.
However, I did have a few problems trying to use this pull, maybe related to python3 that I have to admit I haven't used yet.