In the StartProcessInstanceCommand, the ProcessInstance is saved in the parent NewProcessInstanceCommand but it will not be saved after the Signalling Part of the command.
I think this works more by accident than by design. And it works just because Hibernate is so nice to keep the ProcessInstance in the session and it is saving updates at session close time. But it will not work if you use your own persistence service becasue the save methods will not be called.
In particalur I have the problem with the LoggingService because the logging service does not receive the log(ProcessLog) method call after the signal of the StartProcessInstanceCommand.