The new [channels/radiotray.py](doc/trunk/channels/radiotray.py) plugin allows to bookmark stations from Streamtuner2 directly to RadioTray (or now Radiotray-NG).
It'll require a patch for RT however, so it accepts the proposed DBUS request.
If you want to apply it manually, find `/usr/share/pyshared/radiotray/DbusFacade.py` and add following snippet:
def addRadio(self, title, url, group="root"):
self.dataProvider.addRadio(title, url, group)
Add it after `playUrl` or something. Just take care to keep it coherently indented.
I've opened a feature request [#242](https://bitbucket.org/carlmig/radio-tray/issue/242/new-dbus-method-addradio) for this.
Same for RT-NG: [#92](https://github.com/ebruck/radiotray-ng/issues/92), albeit this moreso requires support from the maintainers (not overly versed with C++).
See also the configuration options, on how Streamtuner2 maps stations onto RadioTray bookmark `<groups>`. Might need more work for Radiotray-NG.