OK, I can confirm that this works with games other than Heavy Rain.
I just updated Mafia II using the same technique and I'd post a tutorial, but I don't have access yet. Below is the run-down:
1. Download the Update to your PC using the PS3 Demo Manager proxy program or from the links provided here.
2. Use the PS3 Demo Installer to create the extra files you need to install on the PS3.
3. Using the instructions that come with PS3 Demo Installer, FTP your update to the PS3 using the FTP server.
4. Reboot without the jailbreak enabled and install the update.
5. Reboot again WITH the jailbreak enabled and start the FTP server.
6. Replace the EBOOT.BIN that got installed from the update with the decrypted one that originally came from the blu-ray disc. It should be located in dev_hdd0/game/(your games serial number)/USRDIR
7. Exit the FTP program.
8. Launch your backup.