While I'm still uncertain as to why the .cuePoints array isn't easily accessible to the videoDisplay or the CuePointManager, I did manage to get to the information another way -- by listening to the metadataReceived event:
videoDisplay.addEventListener('metadataReceived', handler);
and then coding the handler to retrieve the cuePoints via
function handler (ev: MetadataEvent): void {
var cuePoints: Array = ev.info.cuePoints;
...
}

