My guess is BSNL DNS is playing some game here (IIRC they have local DNS for each telecom circle). As for the geekish users, they would know to use opendns, ways to access *.
wikipedia.org etc. But this needs to be looked at seriously. This is not the first time am hearing something like this on BSNL DNS. If we identify the problem, can the chapter / programs do necessary running around for the issue and ensure this doesn't exist?