This incarnation of Mecha Tails made ites first (and last) appearance was when the Bem abducted Sonic, Tails, Dr. Eggman and Snively. Both Sonic and Tails were mechanized into Mecha Sonic and Mecha Tails, while Eggman and Snively were de-roboticized. The Bem used them as part of an experiment to determine if organics were better than robotics. Unsurprisingly, Mecha Sonic and Mecha Tails survived a large explosion, and Mecha Tails kept Snively pinned while Mecha Sonic defeated Eggman. Sonic and Tails were then de-roboticized. (StH: #118)
Later, an alternate Mecha Tails appears as an inmate in the Zone Jail.
By the way
Mecha Tails IS NOT Tails Doll