the files shared with limewire are independant of limewire software, so it's not a matter of LW "supporting" high bitrates. The bitrate of files is dependant on the user who made the file.

If someone has sampled a file at 320 bits then it will be there. The majority of files I've seen run from 128 to around 160. I've seen one 320.

Limewire DOES show bitrate when it's available in the documentation of a file, which is a nice, new feature.