I don't see noise as being an issue at 700MHz or higher though. I understand that some ERP disparity between tower and remote device is necessary, but that's a huge margin.
LTE is based on Code Division Mutliple Access---a wideband noise-based air interface. CDMA has been used by Bell and others for years, with no need for such high ERP base stations. CDMA, by it's nature, tends to require less transmit power to achieve similar results to narrowband technologies like 2G GSM.
I suspect the reason for the high-ERP is related to the test nature of the station. In real world use, 700MHz spectrum propagates very well...necessitating less transmit power. Certainly far less than 1.9GHz or 800MHz.
DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct 91-XG & C5, Channel Master 7777 preamp, Siemens surge protection