The Pecos Badlands are mentioned on pg 98 of Lone Star mentions is where the Psi-X were released.
Page 139 clarifies this is basically just a synonym for the Pecos Empire:
- 2. The Coalition States and the Pecos Badlands. The Pecos "Badlands" (the CS refuses to use the term "Empire") has been a thorn in the Coalition's side for over 40 years.
New West makes a couple references to badlands which might reference it:
- 189 "Just another day in the badlands of the New West."
- 194 "the Western and Southwestern wilderness and badlands,"
Page 136 of Lone Star