In The Dark Knight Rises, Bane reads commissioner Gordon's real speech in front of the cameras before releasing the prisoners. The speech contained the truth about Dent and was Gordon's resignation.
Since Gordon didn't actually read it as he wrote it, how did Bane even know it existed, and how did he get it?
He found it in the Pocket of Gordon's coat when Gordon was his captive down in the sewers. He orders one of his men to search his pockets and he finds the papers containing the speech before Gordon can escape.
He intended to read it on the ceremony in Wayne Manor at the beginning of the film. That's also when the senator gets abducted. Supposedly he still had it in his coat when he goes to rescue him at the bar shortly before entering the sewers.
This is addressed with a little more clarity in the screenplay and novelisation.
Jim Gordon had the draft speech (which he decided not to give) in his jacket pocket. One of Bane's men finds it and hands it to Bane.
BANE: Search him. Then I will kill you.
[The Thug, terrified, pulls out Gordon’s badge, wallet, gun … and the folded papers of the speech he did not read. Bane takes these one by one with quick glances. He stops at the papers. Unfolds them...
As he reads, Gordon rolls off the steps, dropping into the rushing flow of water – gunshots ring out...]
THUG 2: He’s dead.
[Thug 2 trails off as Bane looks up from the papers...]
and
The man held onto Gordon’s gun for a moment longer before meekly surrendering. He put it down, and a look of mournful resignation came over his face. Rummaging through the prone officer’s pockets, he took out Gordon’s wallet, badge, and several folded sheets of paper.
My speech, Gordon realized with alarm. Dear God, no…
The doomed felon handed the items over to Bane, who briefly examined them, one by one. They appeared to be of little interest to him, until he came to the papers. He skimmed the pages quickly, then paused and read through them more carefully. His eyes narrowed.
