I am not a BDO, but from what I have noticed is that they do not start talking to the passenger until the screening begins. They usually stand outside the CP, watch the line/passengers, and if they have someone of interest they will have the TSO at the Mag divert the pax for secondary. ......
interesting comment that the bdo gives the tso at the mag "the hi sign" as everything i've seen (both on the news and seeing someone actually get spotted in the terminal, it has always been with the pax not in the queue but in the terminal (tho they were approaching the security line).
now, careful what you post as you don't know who might be reading
