So...
Parlophone (and "Calderstone Productions") release 50+ year-old (and hitherto unreleased) Beatle out-rakes and broadcast recordings to prevent them from being out of copyright...
Briefly, the much-vaunted extension of copyright in recordings only works for recordings which have actually been released.
For recordings which have never been released, the copyright limit is still "only" fifty years (and presumably must start from the day of recording, since there is no other legally-significant date in the history of an unreleased recording).
This being the case, all hope is not lost for the Rollercoaster tapes...
Briefly, the much-vaunted extension of copyright in recordings only works for recordings which have actually been released.
For recordings which have never been released, the copyright limit is still "only" fifty years (and presumably must start from the day of recording, since there is no other legally-significant date in the history of an unreleased recording).
This being the case, all hope is not lost for the Rollercoaster tapes...