I know that "Alarm" is a GarageBand file as well.
Also, the "New Mail" is used in Mail.app on Macs
Also, the "Tri-Tone" for text messages, would be when the installation wizard is finished installing, when iTunes is finished an operation, etc on OS X.
The "SMS" sounds are just iChat sounds.
So yeah, you can find these around in Leopard, I just do not know where.