I've not tried them nor heard them......but the idea is certainly interesting. The 'bird's tone comes from a narrow humbucker with the magnets as blades rather than under the coil. This gives more singlecoil tone but with fatness due to a series humbucker wiring.
Of course what you have with a full sized humbucker is more girth from the increased width of the 'sensing area'.
^^Interesting signature.
Oh sorry my bad, I've never seen someone put the quote on the bottom before.
Anyway, a Firebird humbucker in a full sized humbucker route is definitely something I haven't had any experience with, but if it delivers I might try a set. I'm wondering how they do it. Does is it a mini humbucker that fits into a full sized route or a humbucker voiced to sound like a mini humbucker?