Sharing animations between models

I actually managed to do this by extracting only rotation info from the anim clip.

1. Make a script called ConvertToRotationOnlyAnim.cs inside of Assets/Editor folder.
2. Add a menu item invoking this script.
3. Import your animation into Unity. (doesn't matter where it's from as long as Unity sees it as animation)
4. Right-click on the imported animation asset and select the menu item we just added at step #2.
5. In the Script, copy over only the curves which have "m_LocalRotation" as propertyName field.
6. Now set the new _rot animation clip to your game object's animation component.
7. Hit play and enjoy... :)

This is the full source code, I posted with some more explanation on my blog.

using UnityEditor;
using UnityEngine;

using System.IO;

public class ConvertToRotationOnlyAnim
{
    [MenuItem("Assets/Convert To Rotation Animation")]
    static void ConvertToRotationAnimation()
    {
        // Get Selected Animation Clip
        AnimationClip sourceClip = Selection.activeObject as AnimationClip;
        if (sourceClip == null)
        {
            Debug.Log("Please select an animation clip");
            return;
        }

        // Rotation only anim clip will have "_rot" post fix at the end
        const string destPostfix = "_rot";

        string sourcePath = AssetDatabase.GetAssetPath(sourceClip);
        string destPath = Path.Combine(Path.GetDirectoryName(sourcePath), sourceClip.name) + destPostfix + ".anim";

        // first try to open existing clip to avoid losing reference to this animation from other meshes that are already using it.
        AnimationClip destClip = AssetDatabase.LoadAssetAtPath(destPath, typeof(AnimationClip)) as AnimationClip;
        if (destClip == null)
        {
            // existing clip not found.  Let's create a new one
            Debug.Log("creating a new rotation only animation at " + destPath);

            destClip = new AnimationClip();
            destClip.name = sourceClip.name + destPostfix;

            AssetDatabase.CreateAsset(destClip, destPath);
            AssetDatabase.Refresh();

            // and let's load it back, just to make sure it's created?
            destClip = AssetDatabase.LoadAssetAtPath(destPath, typeof(AnimationClip)) as AnimationClip;
        }

        if (destClip == null)
        {
            Debug.Log("cannot create/open the rotation only anim at " + destPath);
            return;
        }

        // clear all the existing curves from destination.
        destClip.ClearCurves();

        // Now copy only rotation curves
        AnimationClipCurveData[] curveDatas = AnimationUtility.GetAllCurves(sourceClip, true);
        foreach (AnimationClipCurveData curveData in curveDatas)
        {
            if (curveData.propertyName.Contains("m_LocalRotation"))
            {
                AnimationUtility.SetEditorCurve(
                    destClip,
                    curveData.path,
                    curveData.type,
                    curveData.propertyName,
                    curveData.curve
                );
            }
        }

        Debug.Log("Hooray! Coverting to rotation-only anim to " + destClip.name + " is done");
    }
}