ip.access' 3G-in-the-home blog highlights an interesting comment on Sprint's Airave femto service. Apparently some people have found that while installing Airave improves their Sprint handset performance and indoor coverage, it kills Virgin Mobile connections stone dead.
(Caveat - these comments are all 2nd / 3rd-hand anecdotes, so some harder verification of this would be useful).
The key thing here is that Virgin is an MVNO on Sprint's CDMA network.
I'm guessing that the RF components of the Virgin phones, when in range of an Airave, go "Oooh, what a strong signal, let's attach to that base station!". But then something in the Sprint femto gateway double-checks the provisioning system and says "No. You haven't subscribed to the Airave package, so get lost". And then for some reason the phone can't "see" the other macro cells nearby (interference? something else to do with cell selection?), and disconnects entirely.
It's made me think about the more general problems of MVNOs + host-operator femtocells. This is not something I've heard discussed at any great length, probably because most MVNOs today are 2G, but most femtos are 3G. But going forward, it's going to add another layer of complexity to femto business models and possibly the supporting architecture. It may also prove to be another reason for future femto-optimised handset modifications that involve improved mechanisms for cell selection and mobility.