As reported in Legal Ethics in Motion, a recent opinion of a Texas bar panel concludes that there is no duty to inform opposing counsel that that opposing counsel sent a document containing metadata. Moreover, Texas rules do not prohibit searching for and extracting metadata from documents. Of the nineteen jurisdictions that have issued opinions with specific requirements regarding attorneys’ obligation when transmitting or receiving documents containing metadata, Texas is only the third state to opine that its rules do not require notification to the sender of the document.
For a current survey of the state of the law regarding metadata, check out this page in the ABA's website. For more on the opinion in Texas, go here.