On January 24, 2015, exactly 40 years after it took place, the "Köln Concert" will be broadcast on WDR3 (Germany), at 8 PM. The broadcast will include background information about the concert from Ian Carr and Peter Elsdon.

Thanks to Arnulf for the information.

Update (January 26, 2015). Belgian classical radio station Klara also did a program about the Köln concert and other ECM artists. It's still available here. Thanks to Toon for the link.