I searched the whole file system trying to find the playlists or internet radio station lists, but no luck. I tried to be pretty thorough, with multiple search words. There is only list of default internet radio stations (in .xml), but I checked that it doesn't correspond to the current modified list.

Now I started thinking that maybe the internet radio list is in sqlite database. Could it be? My skills are not enough for searching the database, so maybe someone could do some searching. For example, if it is possible, maybe add a new internet radio station and then search the sqlite database with some string corresponding to the addition.