If your faucet freezes, it will start spraying water and cause a significant water leak. The repair cost can be significant if the plumber has to cut through the wall to repair the water line too. If the vacuum breaker freezes, it will no longer be able to seal the water line tight and prevent a leak. Actually I see the plastic cover splitting or breaking at or near the top screws. That is a sign of deformation and it will eventually fail and leak.
The solutions for all of this are quite simple. The faucets and vacuum breakers need to be insulated. There are home made ways with an old towel and plastic wrap or you can use products that are designed for this and available at most hardware stores.
The faucets can be protected by using an insulated cup or an insulated sock. The vacuum breaker can typically be protected using an insulated pouch which slides over the unit. Sometimes there are water lines coming out of the wall preventing the insertion of a pouch. In those cases, you have to be a bit creative and cover it with some thick fabric and cover everything with a plastic bag. (be aware, wet insulation is not working)