I own both the Region 3 English version of the game and version that has english subtitles and Japanese voice. When running the backup of the latter version, the game did not recognise the save game of the former version. After some tinkering, I found a method to make it work:

Needed: PS3 JB + FTP APP

1. No need to edit any .sfo files.
2. Create a save file in the version of the game you want your save game to work in. (For me i created a new save game within the game for the version with Japanese voice).
2. Browse to the save game folder for the save game you want to enable. (The OLD save game file that isn't recognised. For me this was at /dev_hdd0/home/00000001/savedata/MRTC00003-00) (Note: the 00000001 directory depends on the user account that is used when playing games. I deduced that it follows the numerical order of the accounts under xmb. So make sure to find the savegame file under the user account used when saving the original game file. Also for MRTC00003-00, the "-00" represents the save game number recognised within the game but subtracted by 1.)
3. Copy the APP.dat file and place it into the folder of the new save game folder you made in step 2. Replace the APP.dat in that directory. ( For me, it was /dev_hdd0/home/00000001/savedata/BCAS25005-00)
4. At this stage, the save game utility will not reflect the change made.
5. Start the game and choose to load game. Now, your old save game will appear as "save game xx" where xx is the number of the old file reflected in the old game. For some reason, the new save game you made in step 2 will continue to appear there even though the APP.dat is replaced. Ignore it and load the game file that u need.
6. After loading the game, save the game under a new save file and delete the one you made in step 2. You are now done.