Roughly how long ago did the neighbor build over the alley and attrach to your wall?
What kind of warranty deed did you get for your home? General? limited? Special? The deed should,say...
How do you know the attachment was by permission of prior owner.
That alley ,may or may not be gone forever...but you are way short of,sorting it out .
Lay your deed and the neighbors out on paper..the presence of a spouse's alley may or may not be obvious on paper .