FYI: http://swamplot.com/whats-the-holdup-on-those-half-built-yale-st-condos-by-heights-mercantile/2018-08-10/

Looks like this thing will be tied up in the courts (i.e. blocking the rights of the citizenry) for the next couple years

While this isn't COH's fault that the developer and builder and couldn't get this thing done correctly (no surprise there, though) - it is their responsibility to enforce the rules which require this thing to be in a safe condition. It is unfinished construction work, that's been abandoned, and does not have a certificate of occupancy. The city should require it be returned to the condition it was before, a safe construction worksite, or a structure suitable for a certificate of occupancy. Anything else is a derilict property and the city should enforce as such. The city also needs to make sure anything in the COH right of way is provided to the conditions that are required (specifically, the sidewalk).

Case Closed
Not City Responsibility
The City will restore a sidewalk if it was destroyed by Water or Sewer Utility Work. Otherwise, the abutting Property Owner is responsible for sidewalk maintenance.

Disappointing response from the city. Isn't there a way to compel the abutting property owner to maintain the sidewalk?

The owner needs to maintain their sidewalk!