Sine Waypoint actually doesn't show you how to unlock stuff, which is stupid in itself, this is the only source I have:
Triangulate (Rare) - Unlock: Commendation REQ Pack
I'm 99% done with my Silver packs and haven't unlocked it yet, so it could be true.
Why could that be? Maybe because 343i said themself that Breakout is the least played mode? Oh... I see...
It's mind boggling that they spent so many ressources on Breakout instead of giving us BTB from the get go for example. Just lol at all The Sprint episodes, that focused arround Breakout and how they tested this mode. Such a bad misstep.