It seems that the rhba-7.0-migration-tool.zip (packaged as a part of the add-ons zip [1]) is corrupted, the jars located in its lib folder are different from their counterparts distributed in Maven repository zip [2]. The jars even cannot be opened by a zip utility.

[1] http://download.devel.redhat.com/devel/candidates/RHBA/RHBA-7.0.0.ER2/rhba-7.0.0.ER2-add-ons.zip
[2] http://download.devel.redhat.com/devel/candidates/RHBA/RHBA-7.0.0.ER2/rhba-7.0.0.ER2-maven-repository.zip