According to a post on the official Hatsune Miku Facebook page, footage of the MIKUNOPOLIS concert held at Anime Expo in 2011 will be broadcast on NHK World Premium starting at 12:15 AM Japan time on May 20th. NHK World Premium is a Japanese channel that is carried by many operators overseas and therefore can be watched internationally, either via these operators or by directly receiving the feed via satellite. More info is also available from the Facebook post.
UPDATE: A new post states that the airing time is for the Japanese broadcast and airings on international channels would be at different times.