Nah, just a revamp of the original Ex line. The increased temperature range does not even need new hardware. It is just a software function adding a Range 2 to the camera. Range 2 will have reduced sensitivity though and this is often missed out of specifications
The standard Ex upgrade may work on an XT camera but there is a risk of losing the extended temperature range and this should be considered carefully. If memory serves, an XT owner reported losing the +400C capability after upgrading his camera
That could indicate some sort of model detection or firmware ‘branch’ that is affected by the file changes necessary for the upgrade created by Bud. Note that Bud has never recommended or approved the use of his upgrade files fir use on anything but a standard E4 late model camera running a specific firmware.
Fraser