Rubbish business plan
BT's business plan is to spend more money than Sky to buy the product, and sell it for less than Sky sells it for.
In their 2012 accounts, Sky had sales of £6791m, and a profit before tax of £1189m, a net profit margin of 17.5%. That is a pretty decent wedge of money for Rupert Murdoch, but there is no way BT can offer the sorts of discounts vs Sky pricing that they are proposing. Out of their income, £440m comes from advertising, the rest comes from customer bill payments of one sort or another.
The maths is pretty simple. It costs BT over £19m just to be allowed into the stadium with their cameras. Then they have the costs of actually producing the show - the presenters, cameramen, all the people in the broadcast centre working on the images and sound.
You divide that by the number of people watching the show, and that is how much you need to be able to charge for it to be viable. Whether of course sufficient customers will pay the number you come up with is another matter.