There were a couple of factual issues in the case, such as whether the police department's policy regarding personal communications covered text messages, and whether that policy had been modified by a later staff meeting where a Lieutenant had said that he wouldn't audit the messages as long as the individual employees paid for any overages. However, as described in the Scotuswiki (which did a pretty good job of summarizing the case and arguments), at oral argument, the Supreme Court seemed to be minimizing those factual issues, and coming down pretty squarely against Sergeant Quon. The Scotuswiki cited Justice Ginsburg as indicative of the court's apparent leanings. My preference would have been Justice Scalia, for this characteristically blunt exchange
JUSTICE SCALIA: I guess we don't decide our -- our Fourth Amendment privacy cases on the basis of whether there -- there was an absolute guarantee of privacy from everybody. I think -- I think those cases say that if you think it can be made public by anybody, you don't -- you don't really have a right of privacy. So when the -- when the filthy-minded police chief listens in, it's a very bad thing, but it's not offending your right of privacy. You expected somebody else could listen in, if not him.
MR. RICHLAND [representing the City of Ontario]: I think that's correct, Justice Scalia.
JUSTICE SCALIA: I think it is.
Of course, whether you focus on Scalia, or Ginsburg, or one of the other Justices, the result looks the same - the Supreme Court is likely to decide that, at least for SWAT personnel using government issued pagers, employers are allowed to audit text messages by reading them, even if some of those text messages are personal.