This event will feature live concert of artists, performance of anime cast and showing of specially made new animation (what I think based on the description on the official site ^^;).
To be held on December 31st at Tokyo International Forum Hall A, there will be two rounds of show on that day:
First round: [Climax mission] Show starts 5:30PM
Second round: [Beginning mission] Show starts 10:30PM
The list of anime cast to perform at this event include:
1. Mamoru Miyano (宮野真守 - Setsuna F Seiei),
2. Shinichiro Miki (三木眞一郎 - Lockon Stratos),
3. Hiroyuki Yoshino (吉野裕行 - Allelujah Haptism),
4. Hiroshi Kamiya (神谷浩史 - Tieria Erde),
5. Miyu Irino (入野自由 - Saji Crossroad),
6. Yuuichi Nakamura (中村悠一 - Graham Aker),
7. Ayumi Tsunematsu (恒松あゆみ - Marina Ismail),
8. Arisa Osagawara (小笠原亜里沙 - Soma Peries),
9. Ayahi Takagaki (高垣彩陽 - Feldt Grace).
And the list of artists include:
1. Chiaki Ishikawa (石川智晶)
2. The Back Horn
Admission fee is 7,800 Yen (inclusive of tax) before the event, and 8,300 Yen (inclusive of tax) on the day of the event.
Various official items are announced for the event as well:
Gundam Double O Festival 2009-2010 Official Book - Has introduction of the cast and the theatrical version next year. 2,000 Yen (inclusive of tax)
Assorted set featuring: nylon tote bag, muffler towel, sign light and clear file. 3,000 Yen (inclusive of tax).
Images and information are from the official site.