I think you have it right. Honor points are awarded for non-rated battlegrounds (and world PVP kills, for what it's worth). Conquest points are awarded when you win an arena or rated battleground match. Conquest points are also awarded (in a small amount) if you win the random daily non-rated BG.

Justice points are awarded for defeating the final boss when running a random daily dungeon, up to a maximum of seven such awards per week. Valor points are awarded for defeating raid bosses and if you kill the final boss in the random daily heroic dungeon. Like with Conquest points, the latter is only available once per day.

Justice points can be purchased with honor, at a 125-point loss if I am not mistaken (250 points cost 375 points). And vice-versa. I think you can do the same with Conquest/Valor but am not sure.