PTP is mostly used for industrial control systems that need to have very precisely synchronized timing. The precision you can achieve depends a great deal on the clock hardware you're using. Network hardware, i.e. whether timing in network hardware is deterministic, also plays an important role. So the question is less "what can PTP do," it's more "what can my hardware do with PTP." Fundamentally PTP is just measuring network latency and applying that correction. But the quality of that measurement is critical, and there's nothing PTP can do to mask a crummy oscillator or a switch with non-deterministic timing.