It can not mount PS3VOLUME (which is the Blu-Ray drive) as Blu-Ray disks use UDF2.5!
You can either recompile the kernel with UDF 2.5 support, OR, try this
type -> su (hit enter)
(it may ask you for your root password)
type -> mount -tiso9660 /dev/cdrom /mnt/cdrom (hit enter)
(where /dev/cdrom is the CDROM, and /mnt/cdrom exists as a folder to be mounted to)
Then you should be able to explore it (somewhat) by navigating to /mnt/cdrom
It works on SOME PS3 Games and movies (due to an ISO/UDF bridge!)