Okay, so when I am choosing to landscape from the CS - how do I tell which of the textures have animated grass and which are just flat?

Has anyone made a list of the standard Oblivion landscape textures or is it hit and miss for everyone?

The only way I can do it is to place it and then load up the game and look.
About the only thing I do know, is how to ADD or DELETE animated grass to a landscape texture.

But is there a list of the textures that already have grass applied?

What I'm trying to do is shorten the grass to ankle length,

If a grass texture name ends with NoGrass (such as JMgrassDirtSnow02NoGrass), then it's a flat texture. If it has the word Grass in it but does not end with NoGrass (such as TerrainGCgrass01), then it's an animated grass texture. That's been my experience, anyway.

This is generally the case, aye. There are a few sneaky ones that don't end in "Grass" but do have grass, and do not have a "NoGrass" version either, but they are rare.