Flying to Trinidad regularly in the last few months, I know that CW and WT+ is generally fully booked. It goes via St Lucia, but not many CW get off there as i think many like me are on business. You wont really get that business trade to Tobago so im guessing your fellow CW passangers may well be redeemers too.
As there is a weekly Virgin flight to Tobago, generally with much better deals in Upper Class that BA CW, I think most paying premium passengers would go for that.