After speaking with the Commissioner, the hardest part was finding her way up to the roof; the blueprints she'd accessed of the building didn't account for the changing patterns of the bullpens, or the number of detectives moving around her, or just how to reach the staircase to the roof.
It still wasn't as complicated as the Helicarrier.
Once on the roof, it was just a matter of switching on the signal and standing back, watching it beam into the air - really, the perpetual overcast of Gotham made the bat shadow surprisingly clear. She deliberately kept herself within the soft glow of the signal, even if it made her blind to the shadows; standing at parade rest, she waited to see if the call would be answered.
The light suddenly went out, and she turned to see the darker shadow standing next to the light; blinking hard to clear her vision, she had to admit, that was fast. "Government agencies are known for their cooperation," she told him. "I'll even return his key."
That was as good an opening as she could have planned. "SHIELD is interested in your cooperation as well." And yes, they'd grovel to do so, even if it sat ill in her gut.