Main guy (JPG18) of IER works for LMP2 racing team now as simulation engineer. They are running dir system with ac and csp physics that he coded from ground up...drivers in that LMP2 team use ac/csp to train.
Imo you won't be seeing anything public from IER any time soon maybe ever. (458 GT3 is cancelled)
IER P13C is the most realistic car ever released for any racing game period but that's as far it will go sadly.
I messaged them a few months ago about some stuff and they responded that they were not working on anything for the public at that time which seems to go with the information you are saying. Sad for the general population but I am sure it is good for them. Still enjoy the p13c.