This is stealing her voice. It's just plain wrong.
What I really don't understand is, even if you think AI voice is okay, why not just make an original voice? Why you got to steal somebody's voice? Or if you don't want to do that, why not just get consent for the specific thing you're doing? Don't take advantage of the fact that she previously recorded her voice as an aid for the blind and steal her voice because of some small text in a contract. That's dishonest and pathetic.
You're the railway. Do you know how many people love and obsess over trains and railways? There are probably tons of people who would pay to hear an AI version of their voice coming from the train speakers. How did it come to this? How incompetent can you be?