HI,
when creating new issue for this scenario please link following issue to it as well: https://jira.jboss.org/browse/JBPM-2868
it refers to quite similar case it is just describing smaller scope.
I rough idea - we could add a method that will allow to set operand for query conditions. Either as a new method for the query interface or provide a new method for each condition where user can set what operand should be applied for given condition.