Private companies provide equipment and software to analyse all raw data going through an ISP. All the big names, from US and EU to some countries in Asia, bought this equipment and software.
So, my guess is that a government's budget can enable sampling anything from "so much bandwidth".
Regarding encryption, if you run the numbers, to brute force common encryption algorithms it would take Google's compute 1 second. Image all Google service have an outage for 1 second. Google is just an example to imagine the sizing required. In other words, technically possible. And shouldn't be dismissed with "oh, there is encryption, so that door is closed for any threat actor".
So, my guess is that a government's budget can enable sampling anything from "so much bandwidth". Regarding encryption, if you run the numbers, to brute force common encryption algorithms it would take Google's compute 1 second. Image all Google service have an outage for 1 second. Google is just an example to imagine the sizing required. In other words, technically possible. And shouldn't be dismissed with "oh, there is encryption, so that door is closed for any threat actor".
> Source: I worked on said analytical software.