it looks like the headset is a prototype proprietary headset for traitor. it even says "traitor bike co." on the top race, and they don't sell headsets right now, so who knows exactly how that's set up *shrug*

anyway, regardless you can do this with most any threadless headset, you just have to put your fork/stem/headset together before you run the brake cable through, and if you need to change anything you gotta pull the brake back out. when installing the headset, once you have tightened everything down, it is the stem that holds everything together. the topcap and bolt can really be removed. if you just take out the bolt you can run the cable down through the topcap and starnut down and out. i am more curious as to what keeps the topcap from popping off.

anyway, it's a common misconception that the topcap is there to hold the headset together or that it's some sort of back-up for the stem. a beefy topcap might be capable of saving your ass once or twice, but it's not designed to... and proper bike maintenance (checking your stem's bolts) is a much better safeguard than a mm or 2 of aluminum.