I was in an IT union. It was part of a larger office worker's union. But since I was hourly, if I had to come in for ANY reason outside of my scheduled hours, I automatically got 8 hours but they could also keep me for up to 8 hours, at time and a half. If it was a non-working day (weekends, holidays) then it was double pay for 8 hours.

It worked well because it kept the managers from abusing the employees, and it kept the employees "happy" about it because of the extra pay for not a lot of work.

But every job since then has been salaried professional/exempt and now I'm on call 24/7/365, or 24/7/366 if it's a leap year. I can't leave the state or go on vacation unless I'm "equipped" with company computers with 4g and vpn.