Most of them are on private, but I've heard they get a few every year on the Republican SWA (Bonney Reservoir).
That would be the commanche grasslands units 143,144,139,145...I wish I had some connections down there....The Division of Wildlife is trying to eradicate all feral hogs on public land and, otherwise, officially hope that they don't exist. Good luck.
PS: they also exist down around Kim and Springfield. As well as around Stonewall above Trinidad.