Strategic exit counterfactuals and remedies in Irish retail banking mergers

Strategic exit arises when a business decides to leave a market, but is not necessarily financially failing. As part of the exit strategy, the business may sell its assets, creating a merger situation. A merger which would otherwise look problematic may not give rise to anticompetitive effects if the counterfactual to the merger includes strategic exit. What counts as credible evidence of strategic exit? What happens if the decision to exit is taken after the merger is already in contemplation? Why might a flexible approach to remedies be useful when there is a risk of exit in the event of merger prohibition?