I always considered "DC Challenge!" to be Earth-B's version of "Crisis on Infinite Earths". Which means Kara and Barry survived, and Earth-B must be still around -- somewhere... :wink:
As Earth-B's "creator", E. Nelson Bridwell once said, "wherever 2 or 3 of you gather together in my memory, there will be Earth-B." Or something.
I am not a huge fan of the (Maggin-instigated?) connection between Superman and the Guardians, where Superman is the universal messiah, genetically prepared for millenia as the ultimate Green Lantern, or somesuch thing. For me, it makes explicit too much of the Superman myth. Too literal. I like the smaller references to the GL Corps in the Maggin novels (a Kryptonian was the first Lantern, etc), but that's about it.