The general consesus is that +p is not safe for sistema's. That said, I would not feel too hesitant to use them for defense and a reliability function check. The thing is, there are so many effective non +p .45 loads, I really don't see the need for +p in a 45.
The deal with Sistemas is that they are made using older steels and heat treating methods. Using +P ammo on a regular basis certainly won't blow one up, but you'll see peening of the slide locking lugs and frame rails a lot quicker than you would on a newer gun. Using +Ps for defense is fine, but don't shoot them frequently.