I'm skeptical with regards to the expectation of privacy in a publicly funded office, but that is for the courts to decide. The plaintiffs are demanding trial by jury. That is bad.
I find it interesting that Fox News is not named as a defendant, nor Google since both were instrumental in spreading the tapes around.
I do not think this is going to be thrown out at first hearing. I am also not a lawyer, just a guy with paralegal training.
It could be good. Since the recordings themselves will probably have to be admitted into evidence and shown to the jury, it's possible that one or more members of the jury will be so outraged over the contents that they'll exercise their prerogative to engage in a little "jury nullification" and refuse to find for the plaintiffs.