Earlier this month, the FCC mandated that large carriers such as AT&T and Verizon had to share their data networks with smaller regional carriers---they are already required to share voice networks---such that roaming deals are priced reasonably. As part of this mandate, was a push for interoperability across different bands of the 700MHz network and their associated hardware so that smaller carriers can roam on the different networks of the larger carriers. AT&T and Verizon are not too pleased and cite expense and increased handset size as making this an unfavorable direction.
It's something that smaller carriers, such as Cellular South, look forward to because it will make roaming more affordable. A handset that has a universal chip would work on all networks regardless of what band it's running on in the 700MHz spectrum. There are currently three major bands of the 700MHz spectrum including Verizon's C Block (class 13), AT&T's C and B Blocks (class 17) and smaller carriers A, B, and C Block (class 12).
Qualcomm is planning on a chipset to support class 12 but says that their chips can only support up to two bands below 1GHz and three bands above 1GHz. According to the chip maker, it will be very difficult to support the right combination of bands to allow roaming between AT&T, Verizon, and the smaller carriers. In fact, it's so complicated it could take years to develop. It's not certain when and if the FCC will make a decision regarding this issue.