I really want to use regen as much as possible so if i am coming up on slow moving traffic ahead, i will disengage the CC, to use the regen, but if the car has begun slowing down itself, because of the measured distance, it will use the friction brakes, and when i disengage the CC, it will not use regen at all.
It's like, if it has started slowing down, using the friction brakes, it will not switch to regen braking. I found that a quick dab on the brake pedal will wake it up, and use the regen brake.
To be honest, my fears is that the reason they dont use regen when on ACC, is they made the system to weak, and if the car uses it all the time, the car will break prematurely.