I can't find if it is or not and am very curious - if it doesn't qualify, what functionality does it lack to qualify? I have done a decent amount of batch and don't see any obvious slip-ups in ability.
I believe it qualifies. The basic requirements of Turing completeness are thought to be reducible to a few simple operations, including: the ability to store state (variables), the ability to branch (conditionals), and the ability to iterate (loops). Batch has all of these, so unless there is some as-yet-undiscovered requirement for Turing completeness, batch scripting qualifies.