I remember one of the authority in Subway Town dictating me to pick up the can; Well, I just got started playing Half-Life 2 and I had to do just that so the guard would let me pass. I thought that was odd at that time but now I get it . Although, I didn't pick up the can in Rage so I don't know what the outcome would've been. Perhaps an easter egg o.O?

The guard says 'That's a Good boy' or something like that when you pick up the can in SubwayTown.

Link to Half-Life 2 incident for those who never played/ don't remember;
http://youtu.be/QNd8iNx1gGk

Come to think of it there's quite some similarities in personalities of the Authority and the Combine.

If you try hard enough, you can always somehow make a connection to a movie/game reference

The Shrouded Clan also sound a lot like the guys in white Hazmat suits in Far Cry. In fact I've played a lot of games since FC that have similar voices for anyone wearing chem masks or suits.