Mike Batt included a track on one of his recordings a few years ago, that consisted of one minute of silence, crediting John Cage. The publishers of John Cage's 4'33 sued him, alleging that he had plagiarised Cage's work.

Batt responded in typical style saying that his song is in 4/4 time whereas the Cage work is in a variety of time signatures, and they should specify which part of the piece they believe he has copied...

As far as I know the case didn't get to court- so possibly the work is now traditional?