As I was watching the performance I had some of the same thoughts raised in the Times article. It was hard to believe that they were able to perform so well based on the effect that the weather would have on their instruments. I also couldn't believe that any of them would put their own instruments in jeopardy of cracking.
It is interesting that the organizers of the event chose not to make it known before or during the event but waited until afterwords. It raises a question about "liveness": When Aretha Franklin performed she sang to a pre-recorded backing track complete with pre-recorded backup singers. If the back up was live we never saw the band. Additionally when the Navy Chorus sang the Star Spangled Banner we never saw them (at least not on the CNN broadcast).
In other words, the event organizers made the decision that it was more important to project an image of "live" performance for the quartet than for Aretha Franklin or the Navy Choir. Would it have been acceptable to have Yo-Yo Ma performing alone to the taped accompaniment of the rest of the quartet? I believe this is a reflection of the expectation/delusion of "authentic" performance in classical music that is not an expectation of popular music.