None of our neighbours do it but I have heard recently of the olive strinate. Apparently, during the harvest, the largest olives are placed in a canvas bag with some coarse salt. The sack is tied up with string and hung outside in the cold but sheltered from the rain. It is left there for fifteen to twenty days and twice a day the sack is shaken to prevent the olives going mouldy and to break up the salt.
The frost "scorches" the olives, taking away the bitterness and wrinkling them. They can be eaten straight away or preserved in olive oil with orange peal, garlic and chopped wild fennel.
Olives don't always do well in the cold so it's interesting that the people of the Sibillini Mountains area of Marche have used it to their advantage.