I had a look and indeed they use my base tire grip curves, but sadly they dropped the believable peak slipangles of ~4 degrees which Todd Wasson let slip (gee only re reading do i see the pun!), in favour of uber flexible tires that peak between 5 and 16.5 degrees, which is not possible. Longitudinal slip peaks between 8 and 17% which is also on the high side probably. Load sensitivity was also changed to something I cannot approve, and speed affects grip a bit more than I'd risk putting in but not as bad as most mods. Camber is odd, the front gets 15% more grip at -3 camber, the rear grows 15% grip in just -1 deg of camber.
I'd say the cars won't have too much of that 'overstep limit = spin' behaviour due to the 'better' grip curve, but the car will move around a fair bit due to the flexible peaks. This might look and feel fairly alright, especially considering the poor combined slip physics in rFactor. Probably somewhat like GTR2 did feel a bit like you could yaw somewhat, just not very realistically, and with less over the limit death.
The car also seems very low on downforce if the HDV comments are right, just some ~1100lbs at 150mph at max settings. No idea on the real values, but if it is half well designed, it could have double that..
Notepad ruined most realism out of the tires, but as long as people enjoy it, at least 'my' grip curves remained and might be partly the reason for driving enjoyment