Not sub 700MHz really, more like sub 800MHz
The international designator N28 refers to
703 – 748 MHz Uplink (phone transmitter) 758 – 803 MHz (Downlink - base-station transmitter)
In the UK that sits over the top end of the TV allocation and nudging an ISM band and above that we have the GSM 900 kit. Other countries may well have other things in that spectrum too. Larger antennas at both ends of the link of course, but also to scale with the waventh larger range, and that makes for larger rural cell sizes, fewer sites and power supplies needed. Like TV won't really go over the horizon but is less worried by buildings, trees rain, and all the things that scatter shorter wavelengths.