if you have configured your service with a gateway you can call the gateway.
For example, if you have a JMS gateway configured you can post a JMS Message to the gateway queue.
Most of the quickstarts use this approach, for an example take a look at the jms_router quickstart.
Do you currently have any gateways configured?
You should also be able to use the ServiceInvoker for this. You just need to make sure you have a juddi config on the classpath (juddi.properties + jbossesb-properties.xml) that points to the same shared database instance. You'd also need to make sure the endpoint addressing info is configured such that it's globally addressable e.g. don't use "localhost" etc.