Let me explain the small discovery
Every download that we do on the psn store is a task so we find each task (case) with a specific ID in the path: /dev_hdd0/vsh/task/
Take the example of LBP2 Beta Trial, I finished downloading and I did not installed, it weighs 2133MB
The corresponding spot in the PS3 is as follows:
it retrieves the file with about 2.2GB PKG
but what interests us here are the files d0/d1.pdb open with hex editor.
You see clearly in the name of the software related to the PKG and the address of the download servers from Sony
DL LBP2 Beta Trial: