You can see the perspective/angle of the objects changing slightly as the camera moves in a way that makes it pretty obvious they're CG, AI or otherwise.
That's always been a problem with AI generated imagery in video/animation; it changes too much frame to frame. If researchers figure out how to address that, yeah, we've got a problem. Until then - this looks worse tha
Then there's the usual giveways for CG - sharpness, noise, lighting, color temperature, saturation - none of them match. There's also no diffuse reflection of the intense pink color.
Yes. The lack of diffuse reflection from the pink train is the clearest giveaway, and AI videos in general have problems with getting shadows and radiosity right. There's also the existence of the real-world Hello Kitty Shinkansen and the APM Cat Bus in Japan that makes this image more plausible.
That last point is also important; if it's not surprising, people will just accept it without being too critical about it. And since these AI tools are trained with real / existing content, creating realistic-enough content will be the norm. I think the first big AI generators - dall-e and co - had their model trained on more fantastical / artistic sources, and used that primarily as their model, also because realistic generation (like humans) wasn't yet good enough, or too uncanny. But uncanny and art work well together.
Also consider one of of the reasons AI generated video has CG like artifacts is because it is trained on CG video. Better CG generation, and more real video for training will reduce these over time.
Then there's the usual giveways for CG - sharpness, noise, lighting, color temperature, saturation - none of them match. There's also no diffuse reflection of the intense pink color.