Yes this was introduced 3 years ago with PAN-OS 6.0 :
From the 6.0 release notes :
Support for Syslog over TCP and SSL—The firewall and Panorama now support using TCP or SSL (default is UDP) for reliable and secure transport of logs to an external syslog server. SSLv3 and TLSv1 are supported and the default SSL port is 6514. To separate individual syslog messages in a TCP stream, the delimiter formats available are LF- Line Feed (BSD Format, the default), and Message Length (IETF Format). If the syslog server requires client authentication, you can configure the firewall/Panorama to use a certificate for secure communication. The option to mark a Certificate for Secure Syslog is available in Device (or Panorama) > Certificate Management > Certificates > Device Certificates
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