Create a dynagroup, with a def that creates a compatible group like this:

resource.type.plugin = JBossAS
resource.type.name = JBossAS Server

Now create a group alert on the resulting compatible group.  Now change the dynagroup's definition to this:

resource.type.name.contains = VM

The resulting group becomes mixed.  There will no longer even be an alerts tab.  But the alert you created is still there, you can see it in the Alert Def Subsystem view.  Clicking the link to the alert gives NPE:

java.lang.NullPointerException at org.rhq.enterprise.gui.legacy.action.resource.common.monitor.alerts.config.PortalAction.setTitle(PortalAction.java:114) at org.rhq.enterprise.gui.legacy.action.resource.common.monitor.alerts.config.PortalAction.viewDefinitionRoles(PortalAction.java:219) at sun.reflect.GeneratedMethodAccessor3930.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:597) at org.apache.struts.actions.DispatchAction.dispatchMethod(DispatchAction.java:270) at org.rhq.enterprise.gui.legacy.action.BaseDispatchAction.execute(BaseDispatchAction.java:82) at org.rhq.enterprise.gui.legacy.action.BaseRequestProcessor.processActionPerform(BaseRequestProcessor.java:46) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:236) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:654) at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:557) at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:481) at org.apache.struts.tiles.UrlController.execute(UrlController.java:89) at org.apache.struts.tiles.TilesRequestProcessor.processTilesDefinition(TilesRequestProcessor.java:219) at org.apache.struts.tiles.TilesRequestProcessor.internalModuleRelativeForward(TilesRequestProcessor.java:341) at org.apache.struts.action.RequestProcessor.processForward(RequestProcessor.java:572) at org.apache.struts.action.RequestProcessor.process(RequestProcessor.java:221) at org.apache.struts.action.ActionServlet.process(ActionServlet.java:1196) at org.apache.struts.action.ActionServlet.doGet(ActionServlet.java:414) at javax.servlet.http.HttpServlet.service(HttpServlet.java:690) at javax.servlet.http.HttpServlet.service(HttpServlet.java:803) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.enterprise.gui.legacy.WebUserTrackingFilter.doFilter(WebUserTrackingFilter.java:47) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.enterprise.gui.legacy.AuthenticationFilter.doFilter(AuthenticationFilter.java:129) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.rhq.helpers.rtfilter.filter.RtFilter.doFilter(RtFilter.java:124) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:96) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:230) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175) at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:182) at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:84) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102) at org.jboss.web.tomcat.service.jca.CachedConnectionValve.invoke(CachedConnectionValve.java:157) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:262) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:844) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583) at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:446) at java.lang.Thread.run(Thread.java:619)