Only files that are directly located in the workspace folder of a project on the master
can be copied to a slave's workspace. Specifying relative and absolute paths in the configuration
text field has no effect (e.g. "../build.xml").
The workspace folder also has to be created manually, which is not intuitive.
Several people have reported the same issue on the Copy-To-Slave Plugin wiki page (http://wiki.jenkins-ci.org/display/JENKINS/Copy+To+Slave+Plugin).
The reason for this behavior seems to lie in the FilePath.copyRecursiveTo() method. So this might rather be a core issue.