Tatara successfully shows that it can authenticate a user via a GSM SIM module across a Wi-Fi network without 802.1X: As the press release notes, 802.1X authentication makes it possible to send a variety of Encapsulated Authentication Protocol (EAP) messages across a gateway without special coordination. EAP-SIM is one flavor that some companies favor for using cell phones and cell-based PC Cards with the standard SIM module that's used to handle authentication and billing of GSM phone users.
Tatara's demonstration proves, they say, that they can offer SIM authentication without widescale adoption of 802.1X in public hotspots, but that they can also transition to 802.1X/EAP-SIM when it's available.