The alternative ending we talk about in the report was shot specifically for China and was shown in film theatres there, too. The reason for this was the Chinese censorship agency which wanted Lau to be punished for his illegal activities in the end.
The alternative ending is contained on the Special Edition 2-Disc-Set as seperate bonus material. The runtime of the changes at the alternative ending add up to, including the final fade-to-black, 27 seconds while the original ending is, measured from the point at which the alt. ending starts to differ, 155 seconds, say, 2 minutes 35 seconds, longer.
The runtime relates to the seperate alternative ending!
From 2 minutes 13 seconds on, the changes take place!
Lau walks out of the elevator. There are policemen coming from the right who tell him they knew he was a mole. Lau is being handcuffed.
He looks into the elevator again. Here, the shot of the policeman he shot earlier in the elevator, which is shown in the original ending is missing. He is being taken away.
Lau walks out of the elevator, "greets" his colleagues, then turns back to the elevator, the camera pans. You see the cop who was shot by Lau as well as Yan's body. Crossfade.
Flags are waving in the wind, subtitles are faded-in, saying Yan was a cop.
We're now at policeman Yan's funeral, his former wife, cryingly, attends. Her daughter is present, as well. Lau and other cops salute. After a close-up shot of Lau, fade to the police academy.
Said flashback makes clear that everyone has to keep the rules and if you do not, you will be expelled from school. The instructor asks who wanted to do a swap with Yan. Lau mumbles that he wanted to. In my opinion, a genuine-sad-ironic flashback.
Finally another fade-in of Asian characters, which is subtitled and says that who burns in the eternal hell will never die and that eternal existence was the biggest punishment in hell.