In my experience the Union has not been the road block. They have helped or watched but never stopped us from getting better. Even poorly conceived transitions work if they are honest and persistent. The major road blocks are in the minds of managers. Is it part of a plan to improve the processes used to serve the company.
Action causes attitude.
If management does not have faith in the people it probably won't work. That is part of changing fundamental management beliefs. Communicate direct with the people face to face about why and how. Keep the union informed. Do not undermine the union but do not confuse the union with the people.