the scratch disk settings is defined in the FCP prefs.
so if each user has a separate user account,
they will each have a set of FCP preferences, with a specific scratch disk location.
so if user TIM has a dedicated drive, or partition
and user TOM has one also,
then those drives can be set in their respective preferences.
(BTW, tim, this is the wrong forum for this dicussion, as this is the BUG REPORT forum)
nick