Charlie Stross puts this story squarely in the real world. Sure, it's science fiction. But that only means that it has a fictional element to it. The rest of it reads as real as history. And that's a great thing.
Aside from the inescapable inclusion of Watergate during the last 6 months of Nixon's Presidency, you could be forgiven for forgetting that anything outside of foreign policy even happened between 1968 and 1974.