Regarding the local news station - more likely it was done on a pre-trained model with way more than 25 audio clips. So they would spend hours before hand with a several hours of voice data. And with a single language support for a single person.They are literally used to scam family members, so I assume they are passable. Our local news station demonstrated the exact scam on a high end laptop running a neural net, so I know it's possible.
The ChatGPT-4 OpenAI model can be run locally. You only subscribe if you need the horsepower of the cloud, and lack the needed data. This does not, as far as I am aware.
Secondly, you cannot run OpenAI chatgpt4 locally. You can train your own model using the same algorithm, but the the data they used for that and fine tuning, to get this result is not a generally accessible information.
There's an open source model llama from meta with the data, but:
1. It is not as good at all
2. You would need a powerful GPU (like A100) and enormous amount of RAM to run the 66bln params version to run it smoothly, and still it's nowhere near the OpenAI ChatGPT4.