There is presently a community project that is a feature length film...TWO (TinWoodman of Oz).
And a few more... "Telepresence" (1997) and "Miss Cast Away" (2004) were live action with CG effects movies. I've seen them both. While not GREAT movies, the effects work are good examples of what very small crews with very small budgets can do. With other software it would never have gotten done at all.
There's also a full CG feature called FarStar in production, no finish date announced.
But really, if you're making a feature film, the software you use isn't your main worry. The toughest part is the humungous collection of people you need to get it all done.
AM can import objects from other software, but only as props or converted to the AM model file. If it is converted, you would have to do a lot of cleaning up. AM is not a polygon-based application...the packages you list are polygon-based, so it's harder to go from or to them from AM.
And just to amplify that... In A:M a "prop" is an imported object that you do not intend to "rig" or otherwise edit. You can put it in A:M scenes and move it around. If you need to change it in any way, you should do that in the program it originally came from and re-import it.
If you convert a polygon model to A:M splines, some cleanup will be needed as most polygon models do not have well constructed meshes.
Triangle based meshes are the worst, don't bother with them except as "props".
Quad meshes that came from NURBS or SUB-D modelers have more promise, but a new user would need to understand essential A:M concepts like "spline continuity" and the proper use of unique A:M things like the 5-point patch to properly edit them. These models will not generally be ready to use after simply importing them and substantial editing skills will still be needed.