PS:
It's not that I'm opposed to universe-hopping cosmological mash-ups in general. It's that I don't feel the Eberron setting needs them or benefits from them.
If you have a campaign where multiverse-hopping is expected, that can be fun. GURPS and RIFTS and TORG are all good games based on that premise, and it can easily be encompassed in the AD&D default cosmology as "Alternate Prime Material planes" in a homebrew.
Eberron broke with the default cosmology on purpose, because it had something a bit more specific in mind. And when the designers (including Kieth Baker) rewrote it for 4th Edition, they filed off the last vestigial remnants of the default cosmology. On the first page of this thread, there are some pictures of the Eberron cosmology as given in 3.5 and again in the 4.0 books. In 4.0, the Plane of Shadow (which is included as a shaded sliver below the 3rd ed. Prime Material to account for the spells you cite) has been completely removed.
Take that as an indication of the game designer's intent.
I'm of the opinion that Eberron is cool enough, and varied enough, that you'll be more than happy to toss aside tripe from the Forgotten Realms once you get familiar with it.