I found somemore info about the orchestra in a link from the wonderful U2achtung.com, but it's in Italian...
http://www.rockol.it/news.php?idnews=72531
Here's the freetranslation.com translation...
San Siro, a DVD and an Italian orchestra for the U2
The U2 are about to disembark in Italy, and forecast several surprises for the Italian fan that await the group in the milanese dates of San Siro (20 and 21 July) and Rome (23 July). The before it is a news that moved about unofficial in net in the past days, and was confirmed today from the Universal: the two milanese dates will be filmed from 26 videocameras, driven from Ned OR hanlon and Hamish Hamilton, respectively already producer and producer of the DVD cited to “How to dismantle an atomic bomb” and of the live to the Slane Castle of Dublin turned during the previous tour; destination. Besides San Siro already you were taken again the dates of Chicago and Dublin. “The motive for that we film to Milan is triple”, explained today Jake Berry – director of production of the tour - to the journalists carried to approve the preparation of the gigantic platform: “first, there are two concerts in the same place; second, this stadium is one of the most attractive of the world; third, obviously the Italian public is between the warmest. We hope that these three things moved together allow some special renewals”. To give back even more special the concert were increased the dimensions of the platform, extended from 68 meters to 90, and the illumination. But, above all, the U2 would have convened to the last moment for the milanese date an Italian section of archi, proveniente from the Symphonic orchestra of the theater Carlo Pot of Novara. With the 20 elements the U2 should experience tomorrow to the soundcheck “Original of the species”, piece of the last disk having actual the arcs in the original version. Today it was announced from the promoter Clear Channel the sale of another thousand of cards, possible revenue from the completion of the intense activities of preparation of the platform, that has liberating two areas until now forbidden to the public. The opening of the gates is expected for the 15 (but some persons were already in tail this afternoon), and before the U2 Ash and Feeder will be shown. The U2 should ascend on the platform to 21 about, and to play for more or except for 2 hours and a fourth one.
Well, we can get the jist of it anyway
I think the strings are gonna be super awesome and I can't wait to hear it