Brake lever and shifter for bullhorn
The levers in the first post that you linked to appear to be Cane Creek Crosstop (interrupter) levers. Tektro, Paul, and probably others as well, also make levers like this. They usually work by pressing on the cable housing (effectively making it longer), which is split at the lever. It looks like the levers in the photo are being used as conventional levers and are pulling on the cable itself – the cable appears to dead ends in the barrel adjuster of the levers rather than passing through as it would in a conventional interrupter lever setup.