Technically, they didn't "scam" it because you used a wallet that is not under your control but yes, I believe they will never be able to transfer the coins to another wallet address just because they can't trust you.
If you are lucky to be able to get the private key, then you will have control on your wallet and then you can import it to a wallet software and get the eth; otherwise, nothing you or they can do.
It's not their fault that you can't access your wallet. It's just that simple.
The only thing you can say is BTC-e scammed you, not ethermine