I have to admit that the diverse nature of spectrum holdings and wireless technologies used by mobile network operators in the US keeps me mystified and it's not easy to find out who has what kind of spectrum available. Back in 2011 I did a bands comparison between the US and Europe (see here) and came to the conclusion that there is pretty much the same amount of spectrum available for cellular on both continents. But this post tells little about which company owned which parts in each band. This is where these two posts (see here and here) provide some very interesting background information.
If (or when?) someone starts deploying LTE in the PCS 1900 MHz band, it would be one of the few bands worldwide in which four technologies are deployed simultaneously, GSM, UTMS, CDMA and LTE. Needless to say that manufacturing devices for the US (and for other continents with roaming capabilities) that can be used on more than one network in the US is getting more and more difficult. Also there is some talk of two carriers combining their surplus PCS resources for a common LTE network. Again very interesting from a device perspective as for one carrier such a device would have to support CDMA in addition to LTE while devices for the other carrier would have to support GSM/HSPA + LTE.
It must be happy days for Qualcomm who seems to be the only chipset maker so far that produces basebands that can do GSM, CDMA, HSPA and LTE simultaneously. Oh how I love the spectrum simplicity in other parts of the world :-)