Currently attachments are only collected for Freestyle-Jobs, not for Maven2 jobs.
Stepping into the code I discovered that in:
hudson.maven.MavenTestDataPublisher.perform(AbstractBuild, Launcher, BuildListener)
build.getAction(SurefireReport.class) will return null, so the action is not triggered.

The actions available in build are:

[hudson.model.CauseAction@1460d4b0, hudson.plugins.mercurial.MercurialTagAction@6e3066a8, hudson.scm.SCMRevisionState$None@2ba3d81c, hudson.maven.reporters.SurefireAggregatedReport@3993f896, hudson.maven.reporters.MavenAggregatedArtifactRecord@68daff7b]

none of which is of type SurefireReport.class.

See http://n4.nabble.com/TestAction-not-applicable-for-Maven2-jobs-td1556603.html#a1556603 for the discussion and probably
http://n4.nabble.com/saving-files-with-builds-td1559779.html#a1559779