Sorry guys, the intercept geometry Thirdfain is implying is bullshit. I'll let White Haven sort this out, but here's what the situation will actually look like:
T1 = Time the strike fleets decided to switch targets (League fleet starts slewing a little after the Pirate fleet due to comms delay)
T2 = Pirates and League detect incoming fleet one hour away from Ruda Slaska, while they themselves are minutes away, League decides to run, Pirates follow.
T3 = Strike fleets link up and begin running towards League.
T4 = Defending fleet plots course for nearest intercept (OIP).
OIP = Original Intercept Point
T5 = League fleet swings parallel to course of intercept fleet.
EW = Location of pirate fast sensor ship, ahead of main fleet due to faster drives.
T6 = Chase has been going on for several hours. Pirates detect intercept fleet ahead of them.
There is simply no way you can 'intercept' a fleet that is running away from you at the same speed you are travelling, when they have a one hour head start on you. Strictly there is no way you can intercept such a fleet at all unless they are actually travelling /towards/ you (in the sense of the angle between their trajectory and the line from your original position to their original position being more than 90 degrees; this is basic geometry).
In game terms, if Thirdfain wanted to catch all the enemy ships in one place, he should've launched half an hour later, and they'd all be bottled up in Ruda Slaska (the enemy would be on top of them before they could hyper out). If he'd wanted to save the colony from destruction and prevent the enemy from linking up, he could've launched earlier. For some unknown reason he chose to launch too late to save the colony but too early to trap the enemy. As a result he is going to lose half the system's population and can't catch the fleeing ships in a tail chase. I imagine the next thing that will happen will be the fleeing ships slamming into the interception force - they will desperately try to kill the interdictors before the main fleet arrives, while the Portugese will desperately try to prevent them from doing this.
I personally wanted to go for the 'massive battle in Ruda Slaska' situation. However I generally assume that naval commanders are not grossly stupid and would not chose an option that is patently idiotic, like running on away on a trajectory that allows them to be intercepted. Unfortunately White Haven hasn't been around for me to check, but from his earlier comments I am quite sure he would have adjusted course parallel to the chasing fleet as soon as he noticed them coming after him.