Spectrum as Roads

This is about as explicit as the spectrum-as-land metaphor gets:

"Spectrum is the equivalent of our highways," says Christopher Guttman-McCabe, vice president of regulatory affairs for CTIA-The Wireless Association, an industry trade group. "That's how we move our traffic. And the volume of that traffic is increasing so dramatically that we need more lanes. We need more highways." (Joelle Tessler, "Wireless companies want a bigger slice of airwaves", Associated Press, posted to SiliconValley.com 12/28/2009)

And its also as self-serving as they come.  What the cellular companies need is data capacity.  There are many ways to get that that don't require new radio licenses, notably increasing the density of cell towers and improving antenna technology.  But those are more expensive than new licenses, hence the claim that they need "the land".