hmmm It's been a while and I installed SP1.1 for inventor and SP2 for maya 2013. As a test I imported the sample engine MkII iam and although all the materials imported they did not seem to be applied. The model came in fine though. I am fiddling with it now to see if there is setting or something that has changed.

But all the surfaces (or most) should come in. There are limitations that are explained in the user guide link above.

Depending on how complex the model is if you go iam you'd get the materials you'd just have to reapply them.

Below are images of what gets imported and you can see the materials are all there but you can also see that there is an error applying all of them.

I applied a default lambert so you can see the surfaces are there. Looking at the logs I see a couple surfaces had problems though but for a model of this complexity 99% of the model is there and that's pretty good.