JT,
Mixed Fleet crew are working to very different agreements to current crew, so their working rights are different. They can achieve less time off after trips and trips where current cabin crew and PILOTS would trigger 2 nights down route, like Las Vegus and Hanenda, they only get one night. So they can go into a destination with one set of pilots and leave with a different set because their first set of pilots is having a second night's rest, while they are not.