Accidentially I own both Canon's camcorder (HV10 although) and camera (ixus65 - which I've ported chdk to).And surely the camcorder hacking ideas and possibility of this was an asspain for me from the very beginning ;)
Right now of what I've tracked down, there is actually a firmware upgrade for the XL-H1 and some owners have it on SD cards. We may probably ask someone (
XL H1 Firmware Upgrade Details - The Digital Video Information Network) to share this SD card's content with us.
Minimally, this may give us a clue on how firmware upgrade works.
So, if someone is somehow related to XL-H1 or to people owning it, you may try to help us.
I believe the possibility exists. There is a hack someone found - you may try to press REC and PHOTO buttons in photo mode, and then Power on the camcorder in playback mode. This'll bring up a kind of system screen with internal f/w version and ids. probably it is somehow related with the f/w upgrade.
Surely, there is another way to extract flash memory content out of there. However its a kind of hardcore and requires a special hardware ;)
BTW, head some rumors that the exactly this community (CHDK) could be a reason for canon not to release and allow any public firmware upgrades or information leaks for their HD camcorders ;)