I think they've done a few different versions. The differences seem to be mostly in the TV trimmings at the start and end, and a few versions have US or Canadian civil-defence warnings at the end.

Skimming through, the content seems to be largely the same, but I wouldn't be surprised if they were making small changes too.

[EDIT] Actually, you're right, some of the older versions have different (to my ear, worse) voice work. I'm glad the iterated on the idea and polished it up.