I'd always assumed that the Colossus was secret. The Emperor probably made his speech in front of the contractors, maybe - in any case it was probably recorded for release when the Colossus was unvailed.
Do you not think that the big C would have been mentioned in the game? You know, "keep it up lads, just a couple of weeks till the Colossus comes to save us", etc. Knowing about the Colossus would have inspired the Allies to keep fighting during the darkest days of the rebellion. However, it never got mentioned at all.
Now, presumably Bosch knew about it. Did he a) try to saboage it and fail, b) ignore it, knowing that he couldn't do anything about it anyway or c) he didn't think they'd get it online so fast...