alt Hacker NewsThe 2nd revision of the hardware is 1ns in simulation, likely 5ns in real-world scenarios. The first revision of the hardware (which I saw at NAB) is more like 30ns (with 20ps jitter, I believe).
1ns is about the best you can do with the nearly 1 GHz carrier (as mentioned in a sibling comment).
The limit of a time sync protocol is not generally directly because of the carrier frequency. It can be a lot better or a lot worse depending on many other details. (E.g. the pulse per second from a GPS receiver can give time syncs down to nanoseconds).