It's about the only thing that makes sense. I can't imagine that they'll be flying to Knock when they have so many other holes in their network. It's presumably a link-up with the Manchester flight as they're long gone from Gatwick and don't fly to Birmingham or Edinburgh, which are the other destinations where you can interline out of Knock.
It's a bit unusual to send a delegation just for a potential codeshare though. You could half ask yourself if it's associated with their GAA sponsorship, but Mayo isn't known as a hotbed of hurling...