I have no idea what the materialist atheistic enlightenment may be defined as but since I heard it about a year ago I have loved the Buddha's definition of enlightenment as the end of suffering. Sometimes in my ego, I become convinced I am more enlightened than someone else and then I remember that definition and look at the areas in my life where I am still suffering and happily realize I am not enlightened yet and so yes, I can still expect to suffer and since enlightenment is an all or nothing proposition I can't really be in any position to judge my brother, even if he happens to be a DUmmie.
I've read that one of the reasons Buddhism is incomplete is because Buddha never really dealt directly with the subject of God, as such it may be a more approachable form a metaphysics to an atheist as a means of attaining enlightenment.
I think you are correct though when you point out that without a proper definition of what enlightenment is, it can be a very hard fish to fly. For most people, enlightenment is "thinking the same exact way I do." Especially politically in modern America. Where this falls apart for me is, if I am still suffering then thinking like I do wont bring anybody to enlightenment.
As the classic George Romero movie, Day of the Dead puts it:
Sarah: Maybe if we tried working together we could ease some of the tensions. We're all pulling in different directions.
John: That's the trouble with the world, Sarah darlin'. People got different ideas concernin' what they want out of life.
So, the conclusion I draw from all of this is, there will be no peace in the world until people decide what they want most is inner peace. And since, just like freedom, inner peace cannot be imposed on people from the outside, all plans at enlightening other people will fail. Each of us has the chance to bring one person to enlightenment directly. In light of this, I think the concept of materialistic atheistic enlightenment is flawed simply because the whole philosophy of materialism assumes outer forces working on other outer forces. To be simplistic, many Utopian schemes seem to attempt to bring inner peace by getting people enough stuff and taking stuff away from groups of people who have lots of stuff and giving it to groups of people who have less stuff and it has absolutely nothing to do with enlightenment. Even a materialist who doesn't accept the concept of pure Mind understands that if he stubs his toe, he's not feeling the pain in his toe but in his brain. The body doesn't feel any pain that the mind/brain doesn't tell it to feel.
In the same way we do not suffer because of actual lack in the outer world but because of perceived lack in the inner world. It's not easy, as Einstein said, reality is an illusion, albeit a persistent one. It is the persistent nature of the illusion that makes it so hard to break out of the cycle of suffering because even those times we get the brief insight that we are living in a dream, the dream comes from behind with a boot up our ass and say, "you feel that don't you?" But we all know from experience that just because we seem to be able to see something or touch something or taste something or smell something or hear something, doesn't mean it is actually there.