mashman wrotePLS support has been mentioned a few times on this forum, i'd suggest looking into using them. You can work out the pls file for most stations using tunein's website. i use them in rune in a separate folder from my other music, very nifty.
mm
The 0.3-beta will feature webradios management, letting the user add/edit/delete .pls files (one for radio) via RuneUI. This is the closest way to treat a radio like a single track and get it listed in the Library.