We just received our order of Fuji S5 Pro cameras along with an IS Pro (UV/IR) version. I tried converting the Raw file from the IS Pro with the newest version of DNG Converter (4.3.1, I think) and was unable to. I'm assuming from looking at the camera list that, although this is essentially an S5 with the hot mirror removed, the IS Pro is also different in Raw file and is currently not supported for DNG conversion?
Your understanding is correct. Each camera model must have a profile created for it before it will be recognized by camera raw. I don't know how effective ACR will be working with infrared images. But since you are working with ACR 4.3.1 I would suggest that you take some JPEG images and process them through ACR and evaluate the results. All you need to do is highlight your JPEG images in Bridge and press Ctrl/R to open them in ACR. All of the controls will work.
I have nothing but a recollection of a comment that I remember reading to back this up, but I seem to remember somebody saying that ACR would not be effective with infrared photography. If I'm wrong, hopefully someone will straighten me out.