There was a law passed many years ago that made it illegal to use or manufacture a scanner that was capable of picking up cellular freq's (which lie within the 800MHz band). The manufacturers complied with the law, but made it very easy on some models to "unblock" the cellular band. However, scanners (for the most part) are now nearly impossible to modify to pick up this band, so it's pretty much a moot point.
What makes it even more of a moot point is that this band of freq'svwas dedicated to analog cell phones, which are nearly a thing of the past. Virtually all cell phones are now digital, and using a different set of freqs.
Hope that explains it a little bit...