First off, I do not have any experience with WMIEventProviderNotifications, but I have worked a lot with Service Broker, so I may be totally off, but I think I can still answer this question for you. If I read this msdn article correctly, you are not supposed to read this queue yourself. The WMI provider (which is, according to the article, implemented as a SQL Agent job) reads the items from this queue. The WMI provider seems to provide an API so that WMI-capable clients can query SQL server properties and be notified of any changes therein. Service broker seems to be involved only internally to implement this WMI provider.