It seems to violate the Design Guidelines as stated in the Final Environmental Impact Statement (FEIS) issued by the Empire State Development Corporation (ESDC) and an ESDC spokewoman hinted--though didn't state firmly--that such illuminated signage would be disallowed.
From the FEIS
From page 5 of Chapter 8, Urban Design, of the FEIS:
With the exception of limited signage for ground-floor uses, illuminated and non- illuminated opaque signs would be limited to the westernmost 75 feet of the arena block and to the Building 1 façades along Atlantic and Flatbush Avenues and would be limited in terms of overall surface area and height. Additional signage and lighting would also be allowed on the Urban Room (80-150 feet in height) on Building 1 (to a height of 60 feet), and on the arena façade (to a height of 40 feet); however, this additional permitted signage would have to be sufficiently transparent to make activity within the building and the interior architecture visible to passerby, and to allow people within the building to see outside. This signage scheme concentrates lighting and signage at the intersection of Flatbush and Atlantic Avenues and away from residential neighborhoods to the south.(Emphasis added)
Asked if the pictured rooftop signage would be allowed, ESDC spokeswoman Elizabeth Mitchell repsonded:
Images of the arena used for promotional purposes are renderings. Anything that is built out -- including final signage -- will meet the design guidelines, which we continue to review with Forest City Ratner Companies as specific elements of the design are finalized and evolve from renderings to reality.More images and explanation
In case you were wondering about SHoP's philosophy, the firm describes a Featured Project as such:
Barclays CenterThey may be aiming for a strong connection to the surrounding urban environment, but images like the one helicopter view posted above make the arena look like a petite keepsake, not a (near-) billion-dollar project.
The design of the Barclays Center achieves a striking balance between iconic form and performative engagement with the street. It is legible at multiple scales while maintaining an identity that delights visitors, neighbors, fans, and spectators. Integrated into one of the busiest urban intersections in the New York metro area, the Center will sustain a healthy, interactive dialogue with the surrounding streets and neighborhood. The Main Public Concourse is predominately [sic] glazed at the sidewalk level to ensure optimum accessibility and visibility. The civic gesture of the arena is heightened by a spectacular 30' high canopy which contains an oculus that frames the view of the arena. The Main Public entrance plaza links Atlantic and Flatbush Avenues and creates a flexible, welcoming, yet grand civic space. Views and physical access both into and out of the arena will be plentiful, easy and accommodating, thus ensuring a strong connection to the surrounding urban environment.