Mutavault in simplest terms is all creature Subtype simultaniously, when activated. However Enchantment is a Type, not a Subtype and Mutavault is also not entering the battlefield as a creature, thus cannot trigger Constillation.
After activation Mutavault is colorless Changeling (i.e. all exising creature type simultaniously) and a Land simultaniously.
An example of creature that would Constillation is Courser of Kruphix, which is Type Creature and Enchantment, and Creature Subtype is Centaur.
Edit: Sorry, just noticed the date on the thread.
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Disclaimer: As per the norm, I am aware some people will disagree with my opinion and I acknowledge there is a possibility that my opinion is wrong. The above post is simply my musings on what I view to be the most likely scenario given the information that is available and I am aware of at the time of typing! Peace.