Federal facilities and areas within AZ are subject to federal legislation so they too observe DST.
That's not correct. I'm currently at Pipe Spring National Monument (a federal facility in AZ), and despite being just a few miles from the Utah border, it follows the bulk of AZ in *not* observing DST. I can tell you the same is true for Grand Canyon National Park, Petrified Forest NP, Organ Pipe Cactus NP, and other NPS locations here. On the other hand, Hubbell Trading Post National Historic Site - which is surrounded by the Navajo reservation - follows the Navajo in observing DST. In general, NPS sites in Arizona observe the time of their surrounding areas. I would strongly expect that the same is true for other federal facilities in Phoenix, Tucson, or wherever - it would just be too disruptive for the time zone to be different in a single building.