Day of Mourning - Oct 26

I haven't heard anything at all about this year's event...

Did anything actually happen in previous years, or was it all a load of bollox?

I heard a couple of years ago they did disable mobile phones between 6am and 6pm.

Phones are cut off, there is a message in English for anyone calling into Libya. Sometimes internet is cut, sometimes not.
Flights are stopped, nothing can take of or arrive until after 6pm.

So is it either an official or unofficial public holiday?

It isn't a holiday, work as normal just without international comms.

From what I understand, kids go to school as well, but many wear black to commemorate.