Well it was already modeled pretty well in WITP, although some of these things have been changed for AE (and there are threads about such).
Allies can in WITP (this is not AE specific):
See when Japanese player moves large numbers of planes from base to base.
The Strategic bombing interface gives very accurate details of what is being produced and where. (Although I doubt there were many spies (if any) in Japan at the time, maybe communiques about production were intercepted). I live in Korea, and even now I stand out like a sore thumb. Strategic bombing HI - don't get me started again! (as my facial muscles twitch uncontrollably)
The Allied (asigint), is pretty good, although maybe not as much as some Allied players would like. The Japanese are just blindfolded.
Coastal Watchers give good sightings.
Recon missions are better IMO.
Ports in Japan (and other places) far from Allied bases give good intel of what is in port (number & type)
... there are more, but I might come off as whinging too much
Maybe an AE tester will come and repeat all that has been said about AE, or you could do a bit of a search (which may or may not work).
Sorry for the lack of help, just putting off going to gym
And Japanese players, unlike our soft, lilly loving, fair weather, how can we hamstring the Japanese in AE more cousins -- suck it up cause the war is lost for most of us on Dec 7. (That should get a rise out of some of you!)