After recently watching the director's cut of the first alien film, its quite clear that Weyland Yutani knew about the aliens before the events of that film.
We know that the nostromo was re-routed on their orders, and ash was put on board to make sure a specimen was brought back from lv-426. If all they knew was the beacon was a warning or a distress signal and that it merely could be alien in origin, how did they know it was the type of alien life that you could receive a specimen from? Rather than peaceful, sentient life or what not.
This implies they new a type of non-humanoid life. They knew it must have been deadly or else they wouldn't want it for their bio-weapons division. The decoding of the signal didn't have that specific of a warning did it, if so, why would dallas not have seen the special order, he had access to mother as the captain?
Is that due to weyland yutani's policy of having dallas only see non-science related priorities?
Ash was playing dumb through the movie as well, when questioned what the embryo is, he says he doesn't know and turns off the monitor. The way he looks at Kane and around the room before it bursts out, implies he knew what was going to happen. Sure these points may just be because he found out about what the facehugger was doing once he analyzed it while it was on Kane, but maybe not.
So therefore if the signal from the derelict spacecraft on lv-426 did not contain specific information about the danger, then clearly this implies prior knowledge of the alien was gained by them. Therefore the events in avp-r, would not necessarily break continuity by having the government or certain people in it, be aware of the aliens in some capacity.
