charlie hebdo
So in summary, it seems that the conductor is nominally in charge and that the engineer cannot refuse to accept a conductor on the engine nor "supervise" him or her, all depending on the contract. Correct?
The conductor is, without question, in charge of the train.
As to the relationship between the conductor and the engineer, I go to that of the officer on a fire apparatus and the driver/operator. The officer is in charge of the crew, but operating the apparatus is the bailiwick of the chauffeur.
My takeaway is that (barring further information), you get the crew you drew. However, while you can't outright refuse to work with a crew member (fitness for duty notwithstanding), there are ways to avoid working with a bad apple.
That said, in both a locomotive cab and a fire apparatus, the idea is to run as a team to get the job done. The conductor is in charge, the engineer pulls the handles, but in some tasks - like calling signals, f'rinstance - they are co-equals.