Could it happen like that?
To block bitcoin node traffic the ISPs would need to filter out all traffic doing something called
deep packet inspection for all international traffic. As far as I know only China, with its Great Firewall, and some others dictature-led countries are capable of doing it. I am quite sure India doesn't have this capability. They, most likely, can only blacklist individual IP addresses and domain names.
It can be done, though it does need quite large investment because doing it at high-speed isn't easy.
Adding additional layer of encryption could fix some of the problems. Forming a connection could still be an issue. Basicly lot of things can be blocked on Internet, but these blocks can be circumvented by encryption, VPN and so on...