In a previous life I did it as I was commuting. FO got off plane and asked if I was legal to work the flight up..of course I wanted to get paid for the commute. A quick phone call to scheduling to confirm legality and now I was getting paid for my commute and the other guy was winning by getting to go home about 4 hours earlier. It was that simple and happended during the :45 turn. Delta/DALPA may have some other restrictions/guidelines (we will have to wait for language).

I understand it doesn't work all the time, but its extra flexibility that is nice to have.