And I doubt a lot than a IEM recording comes from the desk, as Dusty said, SBD comes from the desk, IEM comes from the signal transmited from the monitor mixes to the In Ear Monitors that any musician has.
Also there several pro-shot dvds that comes from a satellite interfered signal from the concerts to certains cinemas that broadcasted live concerts, I remember one by Genesis when they did their last reunion tour. IEM recordings must be the same thing, someone catch the signal transmitted, not plugged in the desk.