An opportunity, but not a slam dunk
Operators certainly don't want to be paying the tax to Apple or Google, given that both platforms bite deeply into their traditional revenue streams (look at what iMessage has done to SMS revenues for example, and paying Google when Google are destroying the telco margin model is exquisitely painful for carriers).
However, the carriers are also quite capable of taking a platform and tripping all over it, negating all the benefits of the platform in the first place. The mozilla folks will have to tread very carefully here.