30+ New Dragons (more true dragons than the draconomicon)

[Silverscale]

I might be assuming that some sort of Plane of Faerie is in use.

A perfectly reasonable assumption though it's not in the Core 3.5 cosmology I believe Faerun introduced the Faerie Realm that, much like the Ethereal and Shadow Planes, is both Coexistent and Coterminous with the Material Plane meaning that with the right spells/abilities a creature can pas from one plane ot the other with relative ease.

Coexistent because the Faerie Realm overlaps most if not all of the Material Plane, and Coterminous because there are certain places on the Material Plane where one can step from one plane to the other such as Faerie Circles.