Send in your CV. Based on the response time a computer will scan it for buzzwords and almost immediately accept or decline it (though it's possible edge cases might be passed onto a human - I can't comment). Presumably words like "innovative" or "strategy" will be on the pass list, and so on.
You will then be passed onto an automated Logiks and Factors+ test. These are your standard aptitude tests and a test of you workstyle. It seems a single major weakness in one area is enough for the robot to disqualify you, which should be considered if applying.
Unfortunately, BT does not seem to actually let its applicants know they have been rejected unless they're prompted, though they at least provide a copy of the test results.