They have a few more details that add to the BBC report, as well as clarifying the obvious nonsense in that report that any competent proofreader could have caught ("three-and-a-half-hour masterpiece", "the version of the film he knew was only one-and-a-half hours long", "Around 20 to 25 minutes of footage that fleshes out secondary characters and sheds light on the plot would be added to the film", "round 5 minutes of the original was probably still missing". Can nobody at the BBC do simple arithmetic? "In the 1980s, Argentine film fanatic Fernando Pena heard about a man who had propped up a broken projector for "hours" to screen Metropolis in the 1960s" - Die Zeit has "Mehr als zwei Stunde" which seems about right).

As far as the plot goes, there won't be much that you don't get in the Murnau Foundation restoration, though obviously there will be a huge difference between seeing stills and seeing the actual movie. It sounds like the extended scene with the children escaping from the flooding is the most impressive part. In addition, there is one short scene for which not even still existed until now. The Argentine copy is in very bad condition, so the "new" scenes will always stand out from the old. They contacted the Germans years ago, but got no reply. Apparently they get so many letters claiming rediscovery of the original that they ignore them...

Finally, if you ever hear the movie companies claiming that extended copyright will help them preserve movie history, always remember this. The only reason the complete Metropolis has survived is because an Argentine collector was given the reels after the theatrical run in Argentina ended. Illegally.