The data on this map makes it look like they're going for pretty uniform coverage already. Is there a source for the early orbital planes having a specific purpose? The earth rotates underneath each plane, and the times of day it will be available to any given ground path change over the course of a year.

It does seem pretty convenient that the inclination they've chosen lines the satellites up nearly in a straight path from New York to London, but I imagine this would be relevant to many transatlantic communications.