I should mention that information was gleemed from a 36 page research paper (2006) entitled "Spectrum Policy Wonderland: A Critique of Conventional Property Rights and Commons Theory in a World of Low Power Wireless Devices"
by J.H. Snider, Ph.D.
I just thought it interesting.
It's easily downloadable via a Google search.
Here's a direct quote:
"...As a general rule, unlicensed devices authorized by the FCC are expected to be secondary to licensed devices... The one little known exception where unlicensed devices are not secondary to licensed devices is in the 900 MHz band, widely used for cordless phones, baby monitors, and other simple indoor unlicensed devices.
The 900 MHz exception occurred because of a historical anomaly. Unlicensed devices were authorized first in this band and licensed services only later.
Following its normal practice of protecting incumbents against newcomers, the FCC granted the unlicensed incumbents safe harbor protections against the licensed newcomers..."