Courtesy of justin12 of priusfreunde.de I've got hold of Prius 2 log file with a couple of brakings.
I've identified 2 PIDs that may come handy for brake evaluation
Brake - Regenerative Torque (lbs-ft)(lb-ft)
Brake - Friction Pad Torque (lbs-ft)(lb-ft)
Names are sufficiently explanatory of the 2 braking systems.
Hydraulic braking seems to kick in at 12 Km/h as in the other HSD cars so far.
Differently from Yaris Hybrid, the braking system of the Prius 2 seems to always use some friction pad: look at the beginning of the first braking: there's a small bump in the yellow line, and even when the regenerative system is fully working, the friction value is not 0.
Peak Friction Pad peak value during a regenerative braking is -590080023 while a full effect braking starts at -4425600052.
In the second braking there is an even greater concurrency between the two braking systems.