Does a Medicare PPO Typically Notify when a Provider Becomes Out-of-Network?

I know that an HMO does this (by necessity). If a PPO notices that mb has seen a provider in the past while on the plan, would the company notify the mb of the new out -of -network status of a provider who was previously in-network? It seems to me that this would protect the mb from incurring higher out of pocket costs if continuing with this now out of network provider. Or does the responsibility just fall on the provider to communicate this? Or is it the member's responsibility?

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