There is a building beside my office with a sign board
This building is under demolition
And, this is the sign I have been observing since past 6 months (and who knows for coming months or years)! If I read Demolition in progress, keep away OR This building is scheduled for demolition, I had no problem in understanding that.
Facts apart (whether the builders are in processes or whatever), I'm concerned about the language English here.
Can we use the word 'under' for something that is not happening right in front of you? The process is not ON and nobody knows when it'll be. If I say "under 'x'" all of you will certainly take it as it's in progress. We all know...
This road is under construction- you see the road is getting done, you may find people working on this as well
This building is under construction - you see some constructed part or people working on it.
So, in these latter cases, you clearly find evidence of 'X' in Under [X]. but this is not true in case of under demolition.
Also, are they using the word correctly? Demolition or destruction?