Age of Mythology uses the Bang! engine, designed and developed by Ensemble Studios. The Animation system is custom designed for maximum RTS performance, though it has many similarities to systems used in other games.
As it is a work in progress, there is no way of telling what, if any, model importing, exporting, or other features will be available to 3rd parties.
Sorry for such a non-commital answer, but we have to the finsih the game before we can say for certain how it will turn out.