Statemachine to behaviour tree?

Question

Background

I was able to convert simple statemachines like this...

Into a BT looking like this (Notation describtion)...

root
  sequence  #After another
    playAnimation name:idle
    sequence
      walks? # Breaks current sequence if false
      playAnimation name:walk
    sequence
      runs?
      playAnimation name:run

Goal

But how do we convert more complex multi-layered animation states into a behaviour tree ? How would such a BT look like ? The difficult parts here are transistions between the different states, something i couldnt solve in an BT.

Question

Is it possible to convert every statemachine into a behaviour tree ? What does the theory says and how does it look like in practice ?