[temp.arg.template]/3 contains:

[..] Two template parameters match if they are of the same kind (type, non-type, template), for non-type template-parameters, their types are equivalent (14.5.6.1), and for template template-parameters, each of their corresponding template-parameters matches, recursively. [..]

Following the reference, one might hope to find information on "equivalent types" in 14.5.6.1 ([temp.over.link]). However, while that section does define equivalent expressions and equivalent function templates, it does not appear to define equivalence of types.