When you create a stream with SSE on a sub node of the data store, stream events are not reported. For example subscribe to PCEP Topology within the network topology with:
 

{
  "input": {
    "path": "/network-topology:network-topology/topology[topology-id='pcep-topology']",
    "sal-remote-augment:datastore": "OPERATIONAL",
    "sal-remote-augment:scope": "SUBTREE",
    "notification-output-type": "JSON"
  }
}

 
will not produce any events while subscribing to top "network-topology:network-topology" produces event.

Note that adding optional 'odl-leaf-nodes-only=true' when you get the stream url will work. SSE events are produce as expected.