Depend on what type of freeze they are reporting. We use the terms "Freeze" and "Hard Freeze. A Freeze just means the temps may drop between 30 and 32 for a couple minutes of a few hours. Usually it's not enough of a drop or long enough in duration to freeze water lines with some minimal protection. Hard Freeze means it's below 30 degrees or the freeze will last at least 3 hours. Since most freezes are short (normally on a couple hours below freezing) the average RV's water lines have just enough protection to keep them from freezing.
If you still have a concern, just tape a piece of insulation over any exposed water lines. (that's why you often see some piece of old clothing dangling under an RV) Now, this goes for the metro areas of Phoenix, Tucson or Yuma. Outside the metro areas is another thing as the heat island effect isn't present. Otherwise, thousands of RV's survive freezing temps without any issues even with water in their tank and lines in this area.
by the way, Freon is for air conditioners, antifreeze is for water.
1994 Itasca SunDancer 21RB - Chevy G-30 chassis.