People on Xbox have had challenge lobbies for a long time correct? Yes it is, recently PS3 has been hacked using the device known as PSJailbreak (many ports of this device have been made such as clones, and the 2 famous open source projects PSFreedom and PSGroove)

Since I do not have an Xbox i dont know the exact time prestiging in game was made available, but it is made available by decrypting the file default_mp.self. Ps3 and Xbox have different decryption on these files so even though the Xbob version has been decrypted for some time now the PS3 version has yet to be done.

This is why it is impossible for you to get 11th prestige on a PS3, but please look at this thread posted by IDontBreak:You must login or register to view this content. It clearly shows this person with no prestige/rank icon. The person in questions explanation is he was messing around with Havoc Undead Patch version 6.0, here is video
[ame=https://www.youtube.com/watch?v=kDG3diqNu3Q]YouTube - MW2 challenge lobby PS3[/ame]
(same one in the thread by IDontBreak)

As you will notice the mod menu has the options for what prestige you want, but trying to use these features will not work. Why? because of the default_mp.self file not being decrypted.

This is why it is impossible 9for the time being) for PS3 owners to get in to PRESTIGE lobbies
EDIT:
In this thread i have contradicted my self more than once, in this post I have shown proof someone on PS3 has it, I have seen it with my own eyes by a member one here who i will not name for spamming purposes. So it can hapen it will ust take some time.