Generally, writers do not retain copyright for scripts written for or bought by production companies. Which means those companies have the right to do what they want with the written work. Including, potentially, using the works to train AI.

Companies can train AI on work written by writers in a way that allows them to generate written output that sounds similar to what a writer would’ve written. When this gets efficient and effective enough, expect companies to try to eliminate writing jobs altogether...

WGA is now trying to negotiate a hard stop on use of their members' writing to train AI. This will mean that companies who buy a script or hire a writer can’t exploit writers’ works by training AI to put those same writers out of a job. This is a smart move!