User blog comment:Master Sima Yi/Assassinews 03-03-'13 — Assassin's Creed IV: Black Flag trailer and screenshots/@comment-1153722-20130311074523

It would appear that Edward's memories were extracted from William. They did attempt to extract his memories while he was kept at Abstergo. Would explain how Abstergo found out that the Assassins were in the Grand Temple.

"Oh they definitely tried. But I made things difficult for them. You can resist, you can cloud up the transmission or just refuse to move. Eventually they would have gotten what they needed but still it would have taken them weeks."

And they did eventually get what they needed.