The vast majority of domestic "long distance" calls today would, of course, go over fibre optic transmission systems. There are also some digital radio (e.g., microwave) routes still out there where they make economic or technical sense. Satellite routes are used predominantly for overseas traffic to countries not served more directly by optical fibre transport, or perhaps to some extremely remote locales (in for example, the state of Alaska) which do not have fiber connectivity. Satellite is also still used as backup for some of the submarine cables, should they fail pending repair or perhaps during maintenance [although increasingly infrequently --- since (a) many of the new submarine cables tend to use SONET ring technology which greatly increases availability and minimizes the need to use any sort of satellite restoration, and (b) there is often extra capacity on other undersea fiber systems which can be pressed into service by rerouting traffic over them].
For a historical perspective, check out the URL
Take a look at
Yes. In fact, it was enlarged and moved to a new building a few years ago. For example, see:
Certainly they serve as much of a "PR" (Public Relations) function as anything else. Not to mention the "we always did it that way" factor. And big execs like to build their empires to show off. Certainly, one could debate whether (given today's technology) that all of those people need to be (or even should be) in one physical location.
Depends on your choice of designated long distance carrier, and the extent to which it owns and operates its own facilities vs. buying capacity 'wholesale' from one of the big guys or perhaps a "carrier's carrier" (Wiltel comes to mind here).
Once again, it varies from virtually none to virtually all, based upon who you've specifically selected as your LD carrier. As a very rough first-order estimate, next time you are out on your bicycle or driving around the countryside, take a look at those little signs which are posted along fiber optic right-of-ways ... do you see your carrier's name on many (any) of them ? Certainly that's not a 100% foolproof way to answer your question since there is a lot of capacity swaps & dark fiber/optical wavelength leasing & reselling of bandwidth between carriers, but it may give you a crude sense of who owns what in a relative sense.