You are correct in the unspoken fact (that a lot of the uninitiated are unaware of) that 660 and 880 are still diplexed after all these years. The tower site is in the Bronx.
Find local businesses, view maps and get driving directions in Google Maps.
www.google.com
If you switch to satellite images on that link, you'll see that it's essentially a very small separated part of the island, accessed by a single bridge on Terrace St.; the tower is the only thing there, and would be a hard sell to anyone other than a billionaire who might want to put a megamansion on it.