We know literally nothing about that planet besides of humans live there and it's a part of the Farsight Enclaves.
I can only make an educated guess based on the only books I read which had humans living in T'au territory. The first one is For the Emperor by Sandy Mitchell and the second one is Shadowbreaker by Steve Parker.
For the Emperor doesn't even realy count, because the planet was still under Imperial control. The T'au just started having a presence on the planet and traded with people. The population was kinda divided between pro Imperial and pro Xeno, but for the most part it was just that.
Spoilers: For the Emperor
There wasn't a civil war plot going on..until the Genestealers joined the game.
Shadowbreaker on the other hand is much more interesting. Because here we have a planet that has been Imperial once but got invaded by the T'au who started to terraform it from a dessert world into a green jungle world. The living conditions got better, the T'au are represented as mostly benevolent for both people and planet and most humans loved it. Buuuuuuut humanity isn't known for forgetting about he who sits on Terra. So there was a underground guerilla war going on against the Xenos.
Spoilers: Shadowbreaker
But it wouldn't be a Steve Parker novell if not everyone and everything in the known universe wasn't a monster in some form. The T'au did a lot of researching based on Genestealers on their own population.
So, my guess? I have no fucking clue. It doesn't make sense for there to be any kind of tension. Sorry to waste your time.
The human-murderers are over in the Fourth Sphere of Expansion and afaik something THAT xenophobic didn't happen in the Enclaves. Even without Ethereals around to smooth things out between the factions, we have no reason to believe there are fights happening. I just asume these are humans who lived their lives in the Tau Empire, fought for the Tau Empire and look down on their kin over in the Imperium. They just happen to join Farsight when he oppened his new club. This sounds kinda lame and it probably is lame af, but as long as GW doesn't provide some lore we have to asume it's just another world where nothing interesting happens.