I'm aware of all that .. yes it's not an open service. However, if you have a mobile but the reception in your home is crap, then Femtocell would be a good thing to have. Adding IMEI #'s would be no different that adding MAC addresses to a list for wireless.

It should help reduce battery usage on the phone as the handset isn't straining to get a handle on a crap 3G signal. Much better than running SIP over WIFI. As for hauling the call over my own broadband, I can't imagine the data usage is that high.