You can manage holidays and emergency evacuations in the same way.
At the start of all your vectors have the following step.
goto vector 99 If staffed-agents in skill 99 > 0
after the above line have your vector steps as normal.
The way it works is that you dont use skill 99 except for one dummy agent login which is passed to senior management to allow them to close the centre early or instigate an emergency evac of the building.
The vector 99 simply states disconnect after announcement xxxx.
Have this announcement as a "sorry due to an emergency we have had to evacuate, please call back later" message, but you can change it to holiday messages when you need to use it, or have a similar login for holiday purposes.
To activate the divert simply login to any phone in the building with the dummy login and all the vctors sense that an agent with skill 99 is logged in and divert to vector 99 accordingly.
To de-activate simply log out when you want to open again.
Hope this is clear and that it helps.
John