From the episodes we know that
That there is border area that not part of the nutural zone, as the impression is that "The Tin Man" Takes place in the fronteir where the exact location of the two borders is not set.
Probes are allowed in the NZ, as in the episode "The Neutral zone" (IIRC) the Romulan commander uses the excuse of a robotic probe on why there is romulation communications in that area. Perhaps probes are allowed as mutual technical means to make sure parties do not build bases in the NZ.
That there is border area that not part of the nutural zone, as the impression is that "The Tin Man" Takes place in the fronteir where the exact location of the two borders is not set.
Probes are allowed in the NZ, as in the episode "The Neutral zone" (IIRC) the Romulan commander uses the excuse of a robotic probe on why there is romulation communications in that area. Perhaps probes are allowed as mutual technical means to make sure parties do not build bases in the NZ.