I know the messages get stored in the user's directory under accounts along with the users actuale voice mails. I never tried it but I'm sure you can manualy copy them out if you new witch one's they are.
Maybe some one can write an app. that would auto-extract the voice recording's I'd be so interested in that. Otherwise the voice recording feature is terible.
Just thinking out loud but maybe assign everyone to one group then turn recording on for the the group. Would it just store all of the recordings in the group mail box?