[Psitticine]

The official word, from way back before the game was actually released, is that the only knowledge the AI has that the players don't is the awareness of provincial ownership. As Johan (or Kristoffer) pointed out, that's not a big leap as it is very easy for a human to intuite provincial ownership anyway, and we also have access to the provincial status screen so we always know the relative strengths in terms of numbers as well.

I'd love to say it is a strategy, but I often just forget to move scouts and assassins for awhile. I often come back to find them alone, with no enemy presence about them at all. I've even captured a few provinces with that "tactic," although it was pillage-and-run because I knew my little guy could never hold the place alone.

I realize the results others are getting seem to indicate a certain prescience, but I do firmly believe it is coincidental. The AI tends to shuttle little mini-armies around for whatever reason, possibly for guarding purposes or to avoid supply limits or . . . something. I still haven't figured out what's up with that. Anyway, it is possible that's part of what you're seeing.