Ships of the Star Fleet (Chris Wallace) continuity
Squadrons using the newly-built Penguin-class fighter are sent to serve aboard Al-Burak-class carriers assigned to the Twelfth Fleet along the Federation/Kzinti border in 2231. (The Starfleet Museum: 23rd-Century Carriers and Fighters)
Star Trek: Hidden Frontier continuity
Star Trek: Black Hawk continuity
The Twelfth Fleet and Starbase Twelve is featured in the most recent stories of Star Trek: Black Hawk. Starbase Twelve, also known as Starbase Rockford, is on the Cha'ouwian/Federation Border and takes place after the Dominion Wars at the end of the 24th Century.
Starships of the 12th
The Twelfth Fleet was also the nickname for the Starfleet International chapters based in Region 12 — states of the American Midwest. (Starfleet International: Scott A. Akers, et al., Master Genealogy: Starfleet Region 12)