If you are only tracking locations using the eventbus is in my opinion an overkill.
In my case I am also using owntracks for tracking with mqttitude and mosquitto as a private broker.
I only configured the mqtt transport section (using TLS for authentication):
When I started with owntracks a couple of weeks ago It helped a lot to understand all this by using mosquitto_sub and subscribe to all owntracks topics. It then will show you the exact path where the messeages are going (or coming from) and there you can see that you need the /event portion in your items definition: