I have heard of olive growers doing the same thing.
There is one however that hooks a steam cleaner to his irrigation system when temps are set to be below 19*F for more than a day or 2. Raises the temp in his grove as a whole.
Kinda like using smudge pots to heat the local air within a grove. Florida citrus growers will do that until temps get too low or winds are too high to retain the heat and they are forced to ice everything down.
