Australian Team, We get $20 per day (pre tax) oncall allowance, then time and 1/2 for any work done, time calculated to when you can go back to doing what you were previously. Generally works out to a minimum of 30 minutes overtime for any calls.
If you don't get 10 hours continuous break before the next work day, you fall into fatigue leave and either get paid overtime for the next days work or are stood down till you have had a 10 hr break.
Still doesn't stop our operations team being completely snowed with both workday and oncall work, but they can make a fairly good bonus wage out of it.