A protest over musicians in Zelda orchestra at the Barclays Center: a "non-union building"?

From Kotaku yesterday, Musicians' Union Protests Zelda Concert:

Last night’s 90-piece Zelda symphony at the Barclays Center in Brooklyn, New York drew franchise fans but also a protest in the form of a handful of members of a musicians union and a large inflatable rat.
Local 802, the Associated Musicians of Greater New York, objected to the Tuesday-evening symphony using non-union players. John O’Connor, a vice president for the union, who was standing by the big rat last night toldKotaku that he believed that the group putting on the show, Massimo Gallotta Productions, was using young musicians from out of state and paying them at a lower rate without union benefits.
...The concert’s promoter, Massimo Gallotta, told Kotaku he was surprised that the union protested. “It was so out of the blue,” he said, adding that the performance had been announced months ago but the union had only contacted him last week. “I’m doing the whole tour in U.S., Europe and Canada, and we didn’t have any problems so far. Just New York. The reason I didn’t get union musicians is because the Barclays Center is a non-union building; we don’t have to get union musicians.” For this show he said he used players from Boston as well as local non-union musicians from New York.

(Emphasis added)

The Barclays Center may be a "non-union building" regarding requirements for performers, but it is very much a union building otherwise. And the developer/operator, Forest City Ratner, has always crowed about its commitment to union labor.

Not that there haven't been some union issues in the past.