Are you hearing audio to confirm that these TGIDs are the same agency as TxWARN? TGIDs are unique to a system and even if those agencies are being ISSI or patched to another system, the odd of the TGIDs being the same is incredibly coincidental.
Something fishy is going on but I do not think it is the systems being connected together. Waller CO SO can barely roam into Harris county and has zero need to operate in jefferson county. I also can confirm that SETRRS is nowhere in any of their codeplugs.
On the freqs you are hearing this, please confirm the NAC of the site and frequency.