Sometimes the intel is spot on - at least for the allies. Part of teh game is deciding which intel you want to put stock in.
If you are playing against the AI, you can be assured that "Unit X is planning to attack location Y" is spot on. Against a human it could mean that your opponent has given one of his units that location as its "planning target" but has no intentions whatsoever to actually attack that place. Consider that a "The Man Who Never Was" type intel trick.
If you receive a message "Unit X is on ship Y headed for location Z" you can be assured that this is good intel. Uhnfortunately you do not have any idea of where that ship is in its trip to that location, so it can be a crap shoot if you try to intercept that shipment.
Those above discussed types of messages are for the allied player only. The Japanese player gets "radio transmissions are detected at Pearl Harbor" type messages.
This is where 'you, yourself' need to be... cagier. You may receive that message, and alone, it means nothing. But if you could combine that with other intel reports over various days... it may add up to something.
Assume the Japs have Rabaul, PM, Lunga, but not Noumea, and it's early-mid 42, and these are the intel reports I see.
Day 1 (filtering out the other 20-30 nothings): Heavy radio xmissions reported (120 m S of tokyo - I forget the hex)
Day 3: radio xmissions at a location to the south, that matches an approximate transport travel distance of the day-1 sighting
Day 4: 2nd Snlf is planning an attack on Noumea
Day 5: 1024 men located at Rabaul
Day 6: unit xxxx (Jap division) in planning an attack on Noumea (and lets say the allies know that these two units are together, perhaps from a previous combat a couple months ago or such)
Day 9: Coastwatchers spot 5 ships at Rabaul
Day 13: Japanese Infantry Division is on a ship heading to Port Moresby.
Day 20: 45,000 men located at rabual
Coastwatchers spot 45 ships at Rabaul.
What do you make of that? To me, it tells me that a large amount of japanese troops have moved into the Solomons in force, and he is thinking about going after Noumea.
Or maybe he's just messing with me, and those are reserve troops that are feinting towards Noumea, when he's really going to NE Oz.