You mean in Rogue? That novel suggested Section 31's relationship with the Tal Shi'ar was decidedly one-way and not in the Romulans' favour, its leadership willing to take problematic lists of alleged Romulan agents and look the other way almost long enough for the Tal Shi'ar to weaponize a subspace singularity. Going by Rogue, Section 31's ability to penetrate Romulan civilization is controlled entirely by the Tal Shi'ar. Whatever Section 31 knows about the Romulans is what the Tal Shi'ar lets it know. Good point. Tzenkethi society, though, seems, more xenophobic than Romulan, so that creates all manner of problems.