Mobile operators vs broadband VoIP providers - FMC & mutually assured destruction?

Various mobile carriers are currently looking at ways to block / mitigate / "manage" / measure / bill / generally fiddle about with 3rd party VoIP across their networks.

Similarly, various broadband operators are trying the same thing, with assorted types of deep packet inspection gear being used in anger (or used in desperation, spite or stupidity, depending on your point of view)

I'm not going to rehash this argument again now.... but I do have a specific thought about this when it related to various types of fixed-mobile convergence.

Presumably, it would just as easy for a broadband provider to block a 3rd-party cellular carrier's UMA/SIP/IMS/picocell traffic transitting "their pipes". It doesn't even have to be sophisticated - you could just block all traffic going to another carrier's UNCs or IMS gateways.

I look forward to seeing what happens when (for example....) T-Mobile USA tries to offer UMA-based cellular services over Verizon or AT&T customers' DSL lines....

And I also want to be the first to shout "hypocrites!" at the first operator who tries doing this type of "poaching" when another division of the company is sanctimoniously playing "gamekeeper".