I just got my hands on a conductor (Thanks Sebastian), and after some very early test, can tell you that (on my system), mp3 greater than 192kpbs do not play in the conductor.
My first test was using a file directly imported from amazon, and encoded at 256kpbs. When using it in a show, conductor would start the sequence, increment the time played to '1', get some lights going, and stop right there (less than a second altogether).
On the card that came with the conductor, there was already a music file of the same song, encoded at 192kpbs. I modified the show to use that file and it went without a hitch.
Later on, I reencoded the amazon file to 128kpbs (using audacity), put it back on the card and it worked at that bit rate.
The sequence file (from LSP) had no problem at all.