"Reasonably good" - I watch it and think it's about as good as other ads

There's no requirement that the video be photorealistic. Many ads are animated, if AI can generate good animated ads that counts.

There doesn't need to be any proof or even evidence that these ads are in use. This question is about whether anyone will have demonstrated the capability. This could either be someone specifically prompting it to generate ads and getting reasonably good ones, or an AI system that can generate good video for a wide range of prompts of similar complexity.

If an AI is specifically trained to not generate/be bad at ads but is otherwise good at generating complex video with sound from relatively simple prompts the question resolves yes.