All save games are locked to the PSN account they came from, so if you're not on an identical account to the one the save came from, then no, you can't use any other game saves.
as far as I know it's not possible as your savegame is connected to your system. A friend of mine had to format his PS3 and he couldn't even restore his own game because he used a different user name after the format.
Personally I don't see why anyone would want to copy a save anyway, the whole point of the game is to play through it yourself