Hard to have liability 40 years later. Whether its the engineer, contractor or other professional trades. Many of them are probably retired and the companies of business.
The City / County has liability if they approve or disapprove the remaining building . I would not want to be an owner. The owner’s will have a tough time selling their homes. The will get .25 cents on the dollar from a speculator who will either repair or wreck the existing building and build a new tower with more floors to recover their investment.
See my comment #22 on this thread.