https://www.google.it/search?q=site:m.wikipedia.org finds 636 000 results here. m.wikipedia.org URLs are seen on desktop searches with "normal" keywords as well, mixed with main site.
For instance https://nl.m.wikipedia.org/wiki/Arbeidswaardetheorie, despite its having <link rel="canonical" href="http://nl.wikipedia.org/wiki/Arbeidswaardetheorie" />
Cf. T28115: Interwiki redirects via URL and other 301s are indexed by Google search.