Its the ending location for the wires that come off the ...I forget the name of the part....the swivel link points. One is larger then the other and the wires are suppose to go towards the wheels. I guess they just end right under the them. Looking at the image from your last provided link...thats how they have them. I know that is not the exact car I have but I can't imagine them being two different.
Those swivel links - you are probably referring to the narrow elongated diamond-shaped pieces called the Cylinder Lever, Dead Lever, Live Lever and Floating Lever. All four are components of the Foundation Brake Gear. They are attached by the wires you mention - those are brake rods or, technically, Brake Lever Connections, which are any rods connecting two brake levers. Yes, a brake rod transfers tension from the brake cylinder to the brake shoes via the Brake Beams.
Here is a great discussion that includes descriptions and diagrams of brake rigging (mostly on narrow gauge cars but the general information is valid even today). It is about 1/2 way down the page on my browser:http://c-sng-discussion-forum.41377.n7.nabble.com/Brake-staff-cylinder-confusion-and-mismatched-trucks-td3464.html
Most mortal modelers just left the brake beam end of the brake rod wire end behind the trucks, although there are some advanced life forms who actually model all the linkage, some even make it functional!