Forgive me, but this seems a bit contradictory. You are wanting to encourage RP in-game, but don't necessarily want people to know when the events are to be able to RP in them.
I understand that things don't happen on a hard schedule. This is fine, and I don't have a problem with this because of the way all aspects of the game run. However, IC or OOC, if there isn't a big reward, why not get as many people as possible involved? I know that if there were an event that piqued my interest, I would try to be on at the appropriate time. As it is though, I am rarely on during peak times because of my RL schedule. I may not be your typical player, but if my character doesn't give a flip about an event, I won't bother trying to get involved. For others, who are constantly lamented... the dreaded PLer, they may come and see what this whole RP thing is about. Maybe they will get involved, maybe they won't. The point is, at least a couple of events (may I suggest 1 a month) would be JUST for the purpose of getting as many players as possible involved, regardless of motive. For these events, a schedule would be appropriate.
Also, as a side benefit, the Devs could use this time to test out new GM features or specific game mechanics, or even server/client testing. I don't see a problem if the Devs use this for OOC reasons too.