Not really. Apple can withhold iPhones from carriers if they want.

At best, Google could withhold Nexus phones, they can't withhold Android. Some OEM would always be willing to play ball. I suspect even the compatibility requirements and Google apps agreements wouldn't help. Everything I've heard is that Google certifies phones - not phone/carrier bundles (and, at least in the GSM world, it is hard to see how they could do otherwise).