There may be an easier way, but here is how I do it.
1) drag the radio station from iTunes into Safari. This will drop a playlist file to whereever safari is set to download files.
2) open the playlist in TextEdit, or some other text editing program.
Viola, there is the streaming URL. Copy it into your favorite radio tuner in SL or just set it as the parcel url if you aren't using a radio tuner.
Free SL Radio Tuner at:
secondlife://carmine/103/105/135
or:
htp://www.sweetvitriol.com