Thank you, Varren, for asking two questions I was gonna address, anyway!
The memos themselves are not public, really; it's just my fun way of notifying you players of location changes/new tech through an IC device. Whether or not the Akiri of the Koro wants to publicize the results of the diplomacy is up to them; however, things like the presence of a railroad, in the Po-Koro case, can reasonably be assumed to be common knowledge as they're highly visible. Basically, use common sense about what your character would know.
To answer your second question, the changes described in these kinds of negotiation posts (of which there will be more in the future) can be considered to take place[color=#ff0000;] effective one week OOC[/color] after they're posted. On the one hand, I didn't want to concern myself with thinking up different rolling OOC dates for the results of certain dealings, but on the other, to have their results effective immediately -the easiest course of action- would eliminate a few, well, fun possibilities... One week is an arbitrary marker, but I think it's reasonable.