What does the behavour tree do while waiting for an EQS to finish?

Does anyone know if the EQS node returns fail until the eqs is complete or if the BT waits for the EQS to finish before running the next node in the tree sequence. I looked into the code and I can see the task returns In Progress but what does the behavior tree do with that information?

I believe that, just like when you create your own tasks, the Behavior Tree “sits” in your task until it receives a “Finish Execute” event.