I believe what often happens even if the structure isn’t ‘accidentally’ hit by a JCB or something is that the site is left untouched BUT the buildings on either side are demolished – the resulting lack of support and heavy vibration can undermine and often results in the building being condemned for safety sake.
Achieving the same convenient end result as illegal demolition.
This is just what I’ve been told can happen. This was also related to me about 9 years ago during a discussion re: Temple Bar – strangely enough.