Well, it would be an issue of credit losses leading to failure. That would be an issue of insufficient capital, whereas the only thing a central bank can deal with would be a liquidity issue rather than a credit issue. If you take the situation of the last financial crisis, some jurisdictions activated their swaps with the U.S. Fed because there was a shortage of U.S. dollar liquidity in their jurisdictions. They weren't bailing out any of those institutions, but they were dealing with a localized liquidity crunch and they were lending on a secured basis in order to do that. If you like, it's the kind of conventional central bank response to dealing with a liquidity crisis. Credit losses leading to insufficient capital are a different kind of crisis management exercise.
On February 17th, 2015. See this statement in context.