This seems to only impact some versions of XWiki, not all of them.

On 15.10.6 I reproduced the following:

• installed the publication workflow contrib extension on a subwiki
• in a groovy macro in a job macro, I used the following code:

def publicationRoles = services.component.getInstance(org.xwiki.workflowpublication.PublicationRoles.class)

• ran the job

Expected result

• the publicationRoles variable is initialized to the default implementation of the PublicationRoles class

Actual result

• if the code is surrounded by try-catch in groovy and the error is logged, an error is caught saying

No such property: org for class: Script16
class groovy.lang.MissingPropertyException: No such property: org for class: Script16

This is the error that groovy returns when it doesn't "know" the type passed.