The decision contains an interesting discussion about whether cell phone users voluntarily convey their location to the cell phone company. This is significant from a Fourth Amendment perspective, because information conveyed to third parties is not protected by the Fourth Amendment. This rule applies to, for example, banking records and phone numbers dialed.
In the Texas decision, the court held that unlike bank records or the phone numbers dialed, cell site data is not knowingly conveyed by the cell phone user. This is because, the court reasoned, when a user turns on the phone cell site data is generated automatically by the network.
I am not sure this is sustainable reasoning. While some people may be naïve about how cell phones work, I think there is a growing understanding that a cell phone user may be tracked either through cell tower information or the GPS device built into the phone.