It was 3 years/6 IATA seasons so they will be surrendering the remedy slots to IAG. Even if they lasted the full 6 seasons, they would be grandfathered into only using the slots for any European route, Moscow, Riyadh or Cairo.
As it stands, the only slots they would have to play with are the MAN slots.
Slots won't go to IAG. If Little Red walk away from EDI ABZ, slots, will default to EI to continue those routes.