I think that you might be able too because i think i heard from some magazine that they still had a secret game mode that would kinda be like online co-op thingy with objectives and one team would be covies and the other Spartans. they also siad there would be a coive that could climb on walls. I have no idea if this info is correct so don't take it too seriously
-
large human vs covie multiplayer battles are confirmed but that might not mean you can play as covies