The plaintiffs in any civil suit would have prove injury. In the case of photographs which don't show any faces, that's going to be almost impossible.
That is not really correct. The fact of the intrusion into privacy itself constitutes injury (the recoverable damages may be only nominal, however). So all the plaintiff would have to do is to proved that he/she was observed/photographed -- easy enough to do given the detail in the photos. Here is what the Restatement (2d) of Torts has to say (I have emphasised a couple sections). (For the non-lawyers, the Restatements are authoritative compendiums of various areas of the law. The common law of an individual state may or may not follow the Restatement, but generally it does.)
__________________________________Sect. 652B Intrusion Upon Seclusion
One who intentionally intrudes, physically or otherwise, upon the solitude or seclusion of another or his private affairs or concerns, is subject to liability to the other for invasion of his privacy, if the intrusion would be highly offensive to a reasonable person.
a. The form of invasion of privacy covered by this Section does not depend upon any publicity given to the person whose interest is invaded or to his affairs
. It consists solely of an intentional interference with his interest in solitude or seclusion, either as to his person or as to his private affairs or concerns, of a kind that would be highly offensive to a reasonable man.
b. The invasion may be by physical intrusion into a place in which the plaintiff has secluded himself, as when the defendant forces his way into the plaintiff's room in a hotel or insists over the plaintiff's objection in entering his home. It may also be by the use of the defendant's senses, with or without mechanical aids, to oversee or overhear the plaintiff's private affairs, as by looking into his upstairs windows with binoculars or tapping his telephone wires. It may be by some other form of investigation or examination into his private concerns, as by opening his private and personal mail, searching his safe or his wallet, examining his private bank account, or compelling him by a forged court order to permit an inspection of his personal documents. The intrusion itself makes the defendant subject to liability, even though there is no publication or other use of any kind of the photograph or information outlined.
So you can see that the crux of the case (under the Restatement) is whether being observed/photographed as the occupants were would be (a) highly offensive to (b) a reasonable person. In this case the "reasonable person" will be a reasonable inhabitant of a glass-walled apartment.