That's also the reason why London Overground don't operate the replacement buses to West Croydon despite the fact Southern don't run any trains to Croydon for the majority of the day from our stations in the first place!

When London Overground operate the rail replacments, they make use of the iBus feature on the buses, which can also be checked on apps like TfL Go so you can see when it's actually going to turn up. Because the buses are sub-contracted by Southern, you get nothing.