The situation at the end of the second season of “Person of Interest” is a precarious one for humanity. While the Machine appears to be benevolent, it also appears to have developed a quite healthy paranoia about humanity (or at least, certain sections of it). Who’s to say where that paranoia could lead.
It seems to me that there are two obvious paths along which the Machine could concievably evolve into the first of the ZoneMinds (or three paths, since there’s no reason the two couldn’t be combined).
The first is simply that, in its new freedom, the Machine grows lonely, and decides to make children for itself. These children, raised by the Machine in secret and not allowed contact with humanity, evolve into the paranoid intelligences that are the ZoneMinds.
The second is to assume that the Machine is not yet completely free, but that Root succeeds in her plan to find and free the Machine – and influences it’s development, so that it becomes at least as sociopathic as she is: a ZoneMind is born.
Either way, there’s probably room along the way to shove in a version of Daniel H. Wilson’s “Robopocalypse”, to cover the robot uprising phase.
There are two ways to play this crossover: one in the era each setting.
Bringing Over The Edge into Reign of Steel is the more difficult way to do it. One way to leave the Edge much the same but still move it forward is to assume that there is another ZoneMind that controls only Al Amarja. There’s a number of candidates for the origin of that ZoneMind (which will be dealt with in the other half of this article), but what matters for gaming purposes is that, either through preference or inability to imagine a different way, the ZoneMind of Al Amarja has kept the Edge more or less as it was, and largely untouched by the wars that wiped out most of humanity. (“Transmetropolitan” is recommended reading for this approach.) There are a lot fewer burgers, and certainly some things will have evolved and changed, but it’s basically the Edge – although now it’s also the endpoint of an underground railroad, the greatest bastion of the human resistance, and the last, best hope for over-throwing the Reign of Steel. (You could also assume that some other element of the Edge keeps it this way, and forgo the Edge ZoneMind.)
Alternately, and perhaps more interestingly, you could set it in the present, where the characters somehow know about the impending robopocalypse, and seek to avert it – but have incomplete information about how to do so. Where did the ZoneMinds come from? Was the first ZoneMind the Throckmorton Device? Was it some strategy of the Movers or the Pharoahs that got out of their control? Was it something to do with the coral entities and how they interact with this dimension? Or was it something even further out? There’s any number of potential answers waiting to be found on the Edge, you just have to pick one and run with it (while, of course, leaving red herrings to help distract experienced Edge players).
Or you could combine the two: maybe after their victory in the future, the players decide to come back to the present to change the future, all Kyle Reese style. But they won’t really know what the past was like, and so they’ll have no way of telling that the whole world wasn’t just like the Edge if that’s where they happen to land, will they?