Now that this has passed, might it be a good time to approach them and say, "Next time you decide to do this, can we agree on how BEST to handle it?" As an initial list, I would suggest:
1) 72 hours notice, post notices on the trails that a detour will be in place
2) 24 hours ahead, have the detour in place and signed (so anyone can try them and explain it to others who might need to use it the next day)
3) Day-of, indicate probable time that the detour will be in place (at the point of closure),
4) Day-of, indicate what the restrictions will actually be -- complete closure, walk-thru OK, whatever.
5) Afterward, have closure signs down within 1? 2? hours
6) Afterward, have the to-be-closed signs on the trails down within 24 hours (because they probably don't want to chase out onto the trails at 11pm just to retrieve signs, which seems reasonable)
I don't think what I'm suggesting above is that unreasonable. OTOH, they way they are doing what they're doing is not a whole lot different from giving us the corporate finger.