The relationship between them isn't black and white. Activision isn't a mere publisher where bungie is concerned. Activision loaned bungie a lot of money and got Bungie locked in for 10 years.

I would imagine they (Activision) hold a bit more sway due to the nature of how their relationship started.

But how much control they have and how much they flex, that's unknown.

Their relationship has never really been transparent.

In fact, right when bungie split and a chunk of it stayed with msoft (they became 343) there was this crazy back and forth in regards to the rumors circling the bungie and Activision deal. I've read that Activision payed up front for the 10 year deal. Also read that it was a loan. Also heard it was a super conditional loan full of milestones and rediculous requisites bungie had to hit.

Ultimately, we just don't know.

Look at the ea/dice relationship. Dice is completely owned by ea. EA gets to call major shots there.