I have a close friend who is a pilot for a major professional sports team, operating an MD80. He has come home well, lets just say unhappy, discussing extensively various breeding habits and ancestry of TSO who take longer to "clear" the professional sports team returning from a trip than it took to fly the trip in the first place. So, while he doesn't talk about the details or the extent of involvement, it is clear that they do screen, at least on transport category aircraft in some circumstances. (is the plural of TSO TSO or TSOs?)