How does Intelligence Agent work?

Does it let me see an enemy's maneuver in time to change mine accordingly?

No - it triggers at the start of the Activation phase, after dials are set. It can certainly be useful, but you'll need some other abilities which are used in the activation phase (boost, barrel roll, etc) to exploit the information.

How does Intelligence Agent work?

Does it let me see an enemy's maneuver in time to change mine accordingly?

No it does not. It triggers at the start of the activation phase. All maneuver dials are set.

You get to see the maneuver before any ship activates. Knowledge of that maneuver may help you when choosing your action. Especially when the action changes your location (boost, barrel roll, daredevil). Some ships can even change their own maneuver (navigator, imperial Boba, SoT).

I find the Intelligence Agent very usefull on not so high skill Phantoms. If I know where you are going, I don't mind decloaking befor you actualy move

While in most circumstances the answer would be no, It is possible to change your dial or your movement in response to what you learn from the Intelligence agent

For example if you've also equipped Navigator and / or Stay on Target you will be able to adjust your dial after you have read an opponent's dial - other things to consider might be expert handling on ships that don't have barrel roll, engine upgrade or R7 T1 on ships without boost.

So with the right suite of upgrades you can build a squad that can capitalise on what you learn from the Intelligence agent