The FCC currently outsources a lot of activities including frequency coordination, license examinations, and so on.

They can put rules in place in the agreement requiring free access. I had to remind one of their outsourced organizations of that when I wanted access to their database, it was granted.

AT&T is simply being arrogant.

There is NO technical difference between using an iPhone as a USB or Bluetooth DUN gateway, and using an AT&T sponsored USB cellular WAN device.

They allow the latter so they should allow the former.

Their concern should be the all-you-can-eat data plans that they offer for handheld computing vs notebook computing. They should simply charge a FAIR and competitive rate to what they charge for the USB WAN devices.

If they think, which may be true, that smartphone users will consume even more bandwith than the laptop users would, then simply price the data plan appropriately to allow it while constraining usage as to not negatively affect their network.

I could and did tether my old motorola phones using Bluetooth DUN on the tmobile network, and although slow by today's standards it was nice when I needed it.