In my previous job, the company followed the country's laws pretty much to the letter. Simply being on call gave some small fraction of my "hourly rate" (despite being a full time employee), which actually does add up, since e.g. on a weekend you are accumulating 48 hours of such on call time (while on weekdays it's only 16 per day, as your actual 8 hours worked is not counted twice).

If there was an actual incident, you'd get paid as if that was overtime worked, and it depended on when it occurred (e.g. weekends and public holidays carried a higher than normal multiplier). There were also limits on how much rest you'd need to be guaranteed, etc.

On average, our actual incidents were relatively infrequent, and the pay out mostly depended on the size of the team, which dictated how often you got rotated in. It worked out to something like +10% salary though.