This will be a separate game executable that will not be launched through NBA Elite 11, which would explain the ESRB ratings that popped up last week. A more fully-featured version of NBA Jam will be released on the Wii.
Though EA claims that buying NBA Elite 11 new will be the only way to get NBA Jam on the PlayStation 3 and Xbox 360, I think it's possible that we could see this sold separately at some point. Personally, I'm interested in playing NBA Jam on my PS3 or Xbox 360, but I'm not about to drop $60 on NBA Elite 11 to do so. I am, however, willing to pay $10 or $15 for NBA Jam itself.
Not sold as a standalone, I think EA is leaving money on the table. NBA Elite 11 will be released in October on the PS3 and Xbox 360., while the Wii version of NBA Jam is scheduled for an October 5 release.