I can shed some light on that.

The NZ sony and philips images are based on OzTivo's fine work at revision 1.5. (This is version 3.0 of the TiVo system system)

The NZ thomson is based on the ozTivo 1.3 revision of the thomson software. (This is version 2.5.5 or there abouts of the TiVo system software)