Nope, you can't be a gay lizard man anymore. The multiplayer and campaign are tied in. You'll be a spartan training for God-knows-what in hyperreleastic simulations. Spartan Ops is when you get enough smiley stickers, you get to fight real bad guys, but soon find out that there not that easy to kill.
Not to mention this all takes 4 months after the campaign. The end of the campaign made me :sad: