It's not unusual for small companies in the corporate VIP sector to have flightdeck crew on 24/7 call out, standby duty. I have a couple of buddies who handle this as they only fly an average of 200 hours annually. The AOC in question is in Malta, say no more. Criteria for availability is generally a couple of hours from base, but mostly they get 4 hours plus notice. Booking holidays is normal and if they have consumed alcohol then they are not called for duty. It's their choice and they spend a lot of time at home with family, paid reasonable salaries and are happy in their work or lack of work. Lol.