It seems that the answer to this question:
How to make Facebook page events visible to people who are not logged in.
isn't always relevant. See, for example, this public facebook event:
https://www.facebook.com/events/178688705603659/
which is not visible unless you log in to Facebook first.
Is this a new blanket policy by Facebook, requiring login before an event is visible? Is there a method to enable non-Facebook users to see a Facebook event?