They are now using propane in many smaller units such as reach-in coolers, prep tables (like at Subway), and soda/beverage coolers.
Propane is the basis for just about all of your refrigerants. (I work in a plant that makes/blends aerosol propellants and refrigerants) The different formulations, i.e. R22, R134a, 1234ze, 1233zd, etc., are just highly purified propane mixed with other hydrocarbons to get the desired specifications.
I might use a propane isobutane mix in all my old r12 cars.
If I did, I would say it works fine