I no longer have a NS Bluesbird to test for you, unfortunately.
Most of my Nightbirds came in very LesPaulish cases, but both of my X2000s and my X3000 (Nightingale) came in rectangular cases. The Bluesbirds I have are in slightly different cases than the Nightbirds, but that could be just down to the era from which they came. One of my Nightbirds is in one of those '90s brownish cases if memory serves.
If want to know if something specific will fit in something else specific, let me know and I'll see what I can do.