For single bets it will simply be voided, meaning you will get all of your money back within 24 hours. These events are rare and require that we manually confirm that the game absolutely was cancelled or postponed from official sources, hence the longer processing time.
If the bet is part of a combination, the odds for the cancelled bet will be changed to 1 and the combination will still be active. Changing the odds to 1 means that it has no impact on the total odds anymore and instead only the remaining odds in the combination make up the total odds.