I didn't hear anything about friendly fire involving British Challengers. Was it on the news or on one of the news sites? It is sad when it happens, but it is a dangerous job and no matter what the technology can do and the training it's bound to happen. Hopefully with the lessons from the previous Gulf War, there will be less incidents.
1) Are the Challengers using the same or similiar thing as the American troops?
2) If they are using CIPs and if the CIPs just installed on the back of the turret, I'm guessing it might not be all that effective from the front.
3) According to the maintenance recommendations, it could be possible the sand and dirt are making them less effective.
During Operation ... Wipe the panels with a soft, clean cloth. The panels will need cleaning more often in dusty environments to ensure a strong thermal signature.
Having been out at NTC for almost four years and driven tanks and other vehicles in the desert out there, I wouldn't be surprised if the sand/dust/dirt builds up overtime degrading the effectiveness of the thermal tape. Also with the recent sandstorm, I wonder if it's possible for the thermal tape to become damaged. I remember being out in the desert when the winds kicked up really bad and that's some nasty stuff -- literally sand blasted at times.
I think the effectiveness of these panels will have to be measured by the number of incidents involving vehicles equipped properly with the CIPs.