If you sync with the server the trophies are safed on your HDD, but you cant transfer it between HDDs.
You save the savedata with the ftp-server and with a usb-stick you transfer it to the ps3 with the new hdd. With that method I could transter GOD III savegames. I tried first without ftp and the ps3 said, that the file is protected. Now I can transfer it without problems and the savedata works.
You just have to overwrite the existing files and then you will see the savedata.
Sorry for my english ^^