Only the main award (SPOTY) is voted for by phone. Not sure how rest of the events are done but I imagine at least some of them are done in advance, like the one you mentioned.
In the link given above it says re Overseas winner "Our judging panel of over 30 Sporting experts from a selection of newspaper sports editors (national and regional) and magazines will decide the winner".
Same sort of thing for other awards. But it may be different this year
Reading a bit more it says "voting will only be available by phone - the number to call for each contender will be revealed on the programme after 2000 GMT. There is no voting via the BBC Sport website, email, red button or by text" and "Voting is restricted to UK residents calling from UK numbers".
Last year Mark Cavendish won with 169,000 votes, which was 49% of the vote, so 340,000 votes altogether from the whole of the UK population. It really doesn't seem worth getting too bothered about who wins it.
Who remembers who won in 2010? http://en.wikipedia.org/wiki/BBC_Sports_Personality_of_the_Year_Award