The subbasement would have been a swimming pool. Between the water and Harry's absence it would have become a table with a pewter model of Chicago, no magic left. This was one of the problems with it, ongoing maintenance. And if I believed Jim about anything, somewhere he declared it gone. And unless Marcone got to them quickly nothing on paper would have survived the water damage. Of course that is the real world versus Jim's whims.
But I've always believed that Harry would take it and make it his home before the end. He's going to be owed some favors after this. Marcone especially, since he is the host. Probably the Swartelves and who knows who else.