How do operators handle waste disposal in freezing temperatures?

I run a fleet of standard units, deluxe units with flushing bowls and sinks, ADA-compliant units, and restroom trailers across North Texas. Even here, we get a few hard freezes each winter that mess with waste disposal. The holding tanks in standard units can freeze solid if we don't add brine, and the fresh water tanks in deluxe units and restroom trailers are a real headache, they'll ice up and crack if we're not careful. Pumping becomes slower because the waste thickens, and the hoses can get stiff. I've had to switch to formaldehyde-free deodorizer that works better in the cold. How do operators in colder regions handle this? Do you use heated tanks on your vacuum trucks, or specific antifreeze mixes? What's the protocol when a frozen unit can't be pumped?