Ask bungie.net
Most likely by March 30th - April 10th I'm guessing.
Mythic map pack mythic mature pack
already has been...
No. You either need to purchase it from the marketplace, or you can get the mythic disk when you buy Halo 3: ODST.
The mythic maps are officially coming out on April 9th, read the bungie posts on bungie.net.
All of the maps, including The Mythic map pack 1 and 2, come on the Halo 3: Mythic disk that is included with ODST. If you don't want to buy ODST, I believe that the full Mythic maps are available on Xbox Live marketplace.
The map pack is currently only on the Halo Wars collectors edition. It is rumored to be on xbox live marketplace in about a month
if you buy the halo wars LCE you get a code for the new mythic map pack on Halo 3
it comes with odst
Orbital, Assembly, Sandbox The newer version, the "Mythic Map Pack II," includes Heretic, Citadel, and Longshore
to play the mythic map pack, after its downloaded, go to halo3. then click on custom games and it will load them to the game.
You buy Microsoft points using a credit card or a code then you go to the Xbox marketplace under halo 3 add on's.