If using the build cause condition with matrix project, this fails when using with the conditional buildstep plugin, as the build steps are run in the child builds of the parent build, and these are started with the cause upstream(parent) so all of the checking for other cases.

In this case the we should try looking at the parent build. via AbstractBuild.getRootBuild()

http://javadoc.jenkins-ci.org/hudson/model/AbstractBuild.html#getRootBuild()