Does XiphQT allow one to listen to ogg network streams in iTunes?
Not as such. While XiphQT support for network ogg streams has lately (v.0.1.3) improved significantly (and you can try it in QuickTime Player), iTunes has its own routines for working with network audio streams and broadcasts. However, those routines see every network stream as an ‘MPEG audio stream’. Obviously, this can not work with streams which are not MPEG audio streams. Such as ogg streams, for example.