From a Carroll Gardens Neighborhood Association member, I received a pdf file with a 1999 memorandum from the NYC Law Department on responsibility for the 2nd Place entranceway to the Carroll Street station.
To view the pdf yourself (and it should go without saying, pdf warning for any remaining dial-up users out there), click the hyperlink above. Click the "download file" box on the right side of the page. Click the download box that appears. type in the 4-digit code, and the pdf will open in your browser. Sounds annoying, but takes about 5 seconds.