That's awesome since you have a domain that it actually happened to they should give you an answer. Mine is just a good domain that I'm hoping it doesn't happen to.

Since the types and values of premium domains can vary a lot, I think the ability for a registry to arbitrarily declare a domain as premium presents a huge risk of abuse. I've searched a lot for info relating the rules for premium domains and I've never found anything. I'm super interested to hear what ICANN tells you.