I think you've got it wrong. The information added is that a blue eyed person has been positively identified. In the three person case, each blue eyed person can see two people and is internally modeling their logic about the two person scenario. Once the logic for a two person scenario falls through, they can infer that there are not two people with blue eyes.
The brown eyed people are however modeling an N+1 person case.
Hmm. That seems right. With 3 blue-eyed people, a blue-eyed person observing that the 2 blue-eyed people did nothing does add the additional knowledge that there are a total of 3 blue-eyed people.
So the additional knowledge added for 3 or more blue-eyed people is a lower bound on the total number of blue-eyed people (which grows over time), but it's not exactly clear to me why the foreigner's statement triggers this.
The new information (common knowledge) is added immediately to everybody, not after 2 days. Using this information (that everybody knows that everybody knows that everybody knows...), it is then possible to decide whether you have blue eyes or not after 2 days.
The brown eyed people are however modeling an N+1 person case.