According to the published report, it was also done by two different laboratories and staff. Of course the false positive hypothesis can't be excluded, but the radiographies show the characteristic glass-like pattern of this viral pneumonia.
I still think a contaminated sample is more likely, all else being equal. Not saying this is impossible, but would like to see at least a few other cases this early. If this patient had not been to China then there must be some.
And if this turns out to be a true positive then it indicates the virus is so contagious that it spread that far and wide, that quickly, that overall infection must be much more widespread than is thought.