It is not possible for the government to prevent Bitcoin transactions by censoring the internet. With VPNs and web-proxies being easily available, that will be unpractical. So the only option left is to block internet altogether. It is never going to happen, as there will be widespread anarchy and chaos.
Government can shut down anything they want to shut down. It has happened before and nothing happened. Why do some government countries stops access to some sites, its because they can do it. A government in a country shut down the country's internet for hours because election is going on and they don't want citizens posting updates on the social media but the effect will be haphazard and that is one unique thing about bitcoin and why they cannot stop its penetration and reason why they are now looking for ways around it.
I also agree that the government have the power to control the electricity and Internet itself. If there is a reasonable thing to consider. But if they going to do it to stop the transactions maybe it is not that a big thing to consider for them to disconnect the internet for the both providers and the people who using Internet for personal purposes and transaction through bitcoin. It for me it is possible but it will not happened as far as the system of bitcoin developed and adopt to the changes of technology.