Pianist gets the full score, soloist gets just their own part unless if it's a singer, or if it's an extremely rhythmically difficult piece, in which case it may make more sense for both players to have full scores. Also, it can't hurt to make the solo instrument into a small stave on the full score to help out the pianist.
You guys are both wrong. A 'mode' implies specific pitch arrangements. Music which makes use of all available pitch classes doesn't relay all possible tempered modes simultaneously.
Also, pitch hierarchies exist in much of atonal music.