Good question waren. I reckon it's heavily influenced by organisational culture. A good culture and it's early on. A poor culture and it may be too late!
I think you would have a hard time in any airline avoiding disciplinary action if you refused to take an aircraft that was signed out as legal to fly.
You would want to have a really strong argument and know exactly what you are on about.
QantasLink had that memorable incident where the engineers refused the sign out aircraft because they could prove that the door locks were faulty. Yet the airline and the regulator disagreed.