The CairnsIRIS cameras are normal B/W cameras with IR filter removed so their peak of sensitivity is in InfraRed.
They usually will produce between 350-400 TV lines.
The image is displayed in gray scale and they will be good enough in finding object in environment such as fire.
However, I am pretty sure they will be completely useless in thermal imaging, specially if you want to estimate/measure exact temperature. In this case you can not use autoiris lemses and AGC (automatic gain control). What you use is optical (glass) lens to adjust focus and the rest is done by computer software after image is captured and digitalized.
Now, you can do it much cheaper than $2000. Bye any reasonable B&W camera (Panasonic has good range of low light cameras 0.002lux+/-), price will be somewhere around $300) with CS or C mount Lens. Select 2.5-4mm (wide angle, or fisheye) lens and remove this "blueish" IR filter from the camera.
In darkness you will be able to "see" and what you will see will be "thermal image" of the scene.