I wonder if Keith Smith would know more about this game, as he is mentioned as a source in the history entry. I had only heard of it many years ago in passing; that is, mentioned as a prototype that might have never made it out of the lab (emphasis intentional); and I never gave it any more thought. The description of the gameplay is interesting in that it doesn't match either of our theories.
I've never seen Zap either. Many of Allied's games were scarce here in the midwest; I only remember Paddle Battle and Robot, having played both (and owned a PB board at one time), and perhaps Futsball; at least I THINK I remember that one. I've probably played an EM or two of theirs, but I don't remember for sure.
Regardless, your possession of materials from both games is quite interesting, and an emulation of both games would answer a few questions. I'll ask Owen Rubin if he has any memory of Crossfire, even though its timeline is before he joined Atari.
"One of these days, I'm going to cut you into little pieces!"- Nick Mason, Pink Floyd