"Among the instruments that use treble clef are the violin, flute, oboe, bagpipe, English horn, all clarinets, all saxophones, horn, trumpet, cornet, vibraphone, xylophone, mandolin, recorder; it is also used for euphonium, baritone horn, and guitar (which sound an octave lower)." http://en.wikipedia.org/wiki/Clef#Treble_clef
"Among the instruments that use treble clef are the violin, flute, oboe, bagpipe, English horn, all clarinets, all saxophones, horn, trumpet, cornet, vibraphone, xylophone, mandolin, recorder; it is also used for euphonium, baritone horn, and guitar (which sound an octave lower)." http://en.wikipedia.org/wiki/Clef#Treble_clef
I played the Euphonium throughout school. Used Bass clef the whole time. Hell, even the show uses Bass cleff.
We play the same notes as a trombone, so I don't really understand the treble argument here. Plus, even the show has it in the low brass section. It's just... odd to consider treble with the instrument. It just seems... wrong.
Did some reading - when using Treble clef, you're reading it an octave adjusted and shifted into a different key. I'd personally rather read the notes where they're actually supposed to be...