Here I go beating a dead horse one more time.
When you approach the ergative verb issue from the point of view of active voice, passive voice and middle voice (instead of transitive verb and intransitive verb) you come face to face with the "agent" business.
active I broke the window (I am the agent who broke the window)
passive The window was broken by me (I am the agent)
passive The window was broken (the agent is somebody - unspecified but clearly implied)
"middle voice" The window broke (there is no agent, nor is one implied, nor may one be accepted) designed to please management? ?
"middle voice" The window broke by me (this version is not possible - it's wrong - it's incorrect - nobody would ever say it) management is still safe
ganesh - Would you entertain the possibility that the discussion of agents in your class book may have had something to do with this, rather than agents conspiring to make workers leave?
Very best wishes - A.