OP here. The Ford website lists 2 separate BLIS packages. BLIS with Cross Traffic Alert, which has the sensors in the mirrors, and makes NO mention of towing. BLIS with Cross Traffic Alert and Trailer Tow which has sensors in the mirrors AND in the tail lights.
According to the website, an F-150 gets the first one, and F-250 and better gets the second.
The confusing thing is that the website does not mention towing at all on the first one, and uses the term "Trailer Tow" for the second. My window sticker uses the term "Trailer Tow Monitoring." That does not match either one.
The use of the word "Monitoring" has me thinking it monitors for a trailer and turns itself off. However, the second package is the only one that mentions towing, so I am not sure that it is not the one I am getting.