The 844 prefix lives! As 855 (and presumably everything else) was, test numbers are stored in 250-0xxx. If you happen to find anything interesting, give it a post.
Here's one I found;
844-250-0371 - Routes to your local MCI DMS (or DEX depending on your area). Anything that's ten digits and doesn't start with one or zero will send you to a recording of Deep Note.
Who pushes out updates like this for an entire network? Especially ones that span completely different types of switches