The BBC's charter states that it is not allowed to express a view on the matter: https://en.wikipedia.org/wiki/BBC_News#Political_and_commerc.... Of course, an organisation is made of people and so individuals will occasionally stray from that line (and get called out for it). But they do strive to be balanced on the matter. Here's a link to their "Scotland Decides" pages to give you an idea of how they're trying to balance it out: http://www.bbc.co.uk/news/events/scotland-decides