Yes they use proprietary attachments mostly due to the quick disconnect from the seat. On a somewhat negative look, the attachments don't interchange between sizes, as it would be a waste of capacity to have a 65hp attachment on a 25hp machine.
For my 30hp and 65hp machines, I made adapters to go to standard skid steer and also the mini coupler as the purchase price of generic tools can be cheap from places like Titan where I bought my flail shown in previous post's pictures. Just an FYI, I have attached a pic of the PT to skid steer adapter I made.
If money was no consideration, I would have a A Carraro, but I fix all my own equipment and a hydro Italian tractor needs factory training to get in deep. The PT is just a pump and motor and easy to replace. Unfortunately only one range.
The first PT I bought for brush work about 5-8 years ago, was the PT180 for $5500 (before building back better). For that price could you walk into a John Deere dealer and come out with a new tractor with 4x4, power steering, loader w/quick attach?
The older PTs had a rear PTO and 3pt, but they found once you use the front quick attach, there was not much reason to use the rear 3pt. You can change a front attachment in less then a minute if no hydraulics, so why fumble with a rear attachment you cant see well?