I've been poking at the site a bit, and I think...probably you could? You'd wind up skipping the very first few steps, or altering them, since those are where she has you starting to build the physical world itself (especially true if you're doing urban fantasy in an altered Earth). But the later steps start asking things like "how does your magic work? what can't it do? what kind of races live there? how much education do most people get?" And stuff like that would be useful anywhere. :3