I didn't try all objects available in Armagh 3. On video two objects, a big dome and a high grass. These objects, (and similar) are often used for masking of equipment.
When your equipment hot and the engine didn't cool down yet, it is natural that in the thermal imager it is possible to see hot elements of the car. The artifact is as follows. The medical logo is illuminated and is visible on outer side of objects for which the medical truck is hidden.
https://www.youtube.com/watch?v=3BWRmtNdU3w
https://www.youtube.com/watch?v=SA8c7HEAIRo
There were situations when the logo was well visible through masking, and by cold car.
http://stroybat.ucoz.ru/raznoe/Texture/2015-07-22_00005.jpg
http://stroybat.ucoz.ru/raznoe/Texture/2015-07-22_00006.jpg