I think BA can do what they want with the slots ,if returned.
Not sure what situ is if someone else wants to have a go e.g.Aer Lingus had originally applied ,in competition with VS ,to op Abz/Edi in their own right, so they might be interested.
The Man slots are already owned by Vs so they could use them as they want, but I guess we need to give VS a chance rather than speculating before the services have even started.