I think the real trick isn't convincing hardware makers -- they do what the operators ask them to (at least in the non-Apple world). Operators like Telefonica are interested. See e.g. http://blog.mozilla.org/blog/2012/02/27/mozilla-in-mobile-th...
They know they have unique infrastructure capabilities and, to their credit, want to create additional value to end-users. In conjunction with their current purchasing power and influence over hardware vendors, forward-looking mobile carriers can definitely view B2G as a possible competitive edge if they can figure out how to bring one to market in the most cost-effective (read: cheapest and least disruptive) way possible.
It's a breath of fresh air considering the capabilities and branding that Mozilla has. I would love to be a fly on the wall in those discussions.