The format itself seems pretty simple, in Steve-m's RW Analyzer I did some looking through a handful of .anm files, I have posted what I found in one below, each was nearly identical (except with HEX ofcourse):
The file format doesn't have much of a structure, all it is is [0x1B] Anim Animation, and thats all that there is in it's file. Whether this means it would be easier to successfully open and decode or not, I don't know just yet.
Okay, some other stuff, the HEX and the The Tree Structure...
|Anim Animation (53120 bytes @ 0x0C) - [0x1B]|
--> Too big to post here -->
Now theres nothing much there in the HEX that jumps out at me, but from the weird symbols and odd dot (.) locations, it reminds me of animation flies such as Graphic Interchange Format (.GIF) which looks similar when view in a text editor. Steve-m said to me over PM that it does only contain one section (as stated above), which is the Anim Animation. DexX did some work with the file format awhile back (which work on UV anims) here.
I'll continue to look into this, but I'm not sure how I am going to go about decoding it yet. From what I have found so far, it should end up pretty simple if we're luck.