Network policy management and "corner cases"

I've been speaking to a lot of people about policy management recently, fitting in with the work I'm doing on mobile broadband traffic management, as well as the Business Models aspect of my newly published report on Broadband Access for Telco 2.0.

A lot of what I hear makes sense, at least at a superficial level. Certainly, I can see the argument for using PCRFs to enable innovative tariffing plans, such as offering users higher maximum speeds at different times of day, or using DPI or smarter GGSNs to limit access by children to undesirable sites.

But there's a paradox I see on the horizon. In the past, telcos (fixed and mobile) have been pretty obsessed with corner-cases. "What happens if a user tries to set up a 3-way call while they're switching between cells?", "What happens to calling-line ID when I'm roaming?" and so on. Sometimes this is because of regulatory requirements, sometimes it's because they're worried about the impact on legacy systems not being supported - and sometimes it just seems to be preciousness about some minor complementary service that nobody really cares about.

So what happens with *data* policy management and corner cases? What happens if I'm roaming and the local operator's policy conflicts with my home operator's? Do I get a subset or a superset? The lowest common denominator, or some sort of transparency? Imagine my home operator allows VoIP on its mobile broadband, but limits YouTube viewing to 100MB a month. But the visited network doesn't allow VoIP for its local customers, but also doesn't have the ability to discriminate video traffic - or, perhaps, applies some sort of compression via a proxy. Sure, everything might be backhauled via my home network.... or it might be offloaded locally.

[Side question - what happens to international data roaming traffic on a visited operator that does WiFi offload, provided by a separate managed offload operator?]

In a nutshell, I guess this boils down to "Policy Interoperability". And a need for policy IOT testing, on an ongoing basis. I strongly suspect this won't be as easy an many think.

Whether the "corner case" problems impact the overall use of policy management will probably depend on hard problems around with local regulations and laws, I suspect. But as a customer, will I really be happy with having the most stringent superset of policies applied, if there are multiple operators involved in my providing my connectivity?