I think the clue is in the term "wet leased" there may not have been any Monarch staff on the aircraft at all. Monarch have been wet leasing aircraft for years. Some time ago, we were booked on a Monarch flight to Faro. Instead of the Airbus, we were shepherded on to a an ancient (even then) Tri-Star. The Icelandic crew were fine but the the aircraft was knackered. We arrived on time, which is more than could be said about the return flight. They kept us waiting twelve hours as they used "our" designated aircraft to replace one that had gone tech at Malaga which should have flown to Goa.
The relevance of the aircraft ownership at Birmingham does not carry too much weight. Someone cocked up and in the fullness of time we shall find out who that was. This particular aircraft has had a chequered life since it has been working for Monarch, but hey! It could have been Algerian!