I would think PT uses what is available for best price at the time. I know I needed a part for a motor on a mower and had to send pictures of the hyd motor. Indicating to me they used a least more then one motor.
I have PTO driven implements and I only have one that is PTO driven to hydraulic, a boom mower. I think back hoes would fall in same category. This is mainly because tractors tend to have smaller hydraulic pumps and use the mechanical PTO to power implements directly. PT have a least 3 pumps, one like normal tractors to power steering and loader, one to power just the implement and one for the drive system.