I don't think there is any rule that new trains can't be started during model code of conduct. Model code of conduct started on 16th March and 03546 Andal Bardhaman new Memu service (not a extension or any spl train as the no suggests, it is a permanent train which is running with spl number just like all other memu trains in India) was started from 24th March. The only restriction is that no political personality can arrange or take part in any inauguration event.
But yes, this new Ranchi Varanasi VB news, to be inaugurated within a few weeks as claimed by this article, seems to be a spicy news that hardly has any basis.