The new Modern Warfare 3 maps Shoot Me and Shoot Me a Bit Harder are only accessible by the Xbox 360 Gamertag that subscribes to Call of Duty: Elite.
The problem being, this appears to contradict the stated terms of download.
Those terms state that, "The item you are trying to download is subject to usage restrictions. You can use this item on the first Xbox 360 console you downloaded it to. Access to this item will also be granted to all users on this first console."
This issue, however, may never be rectified.
One MW3 forum member claimed to have contacted Activision. Said person was told that the premium Elite maps - Liberation and Piazza - were, yes, locked to one Xbox Live Gamertag. And Activision apparently didn't know if this restriction would be lifted when the maps are released to all in March.
Also, as members of the MW3 forum pointed out: the maps can be played in split-screen, providing the Elite-subscribed XBL account leads the playlist. Perhaps that's what the usage terms meant.
An annual Call of Duty: Elite membership costs Ł34.99.