Attempting to withdraw XPY to a BTC address will result in an invalid address error.
The coins, in the end, stay in your account.....unless they have been removed by site owner after request (which I have actually seen done by paycoinpoker admin while claiming they got lost in cyberspace)

I've tested this over and over again. XPY will never send out into "cyberspace" when accidently withdrawn into a bitcoin account. The end result is just the network won't recognize the transaction. Another member has complained they accidentally withdrew their XPY into a bitcoin wallet, and paycoinpoker response was "oh well your mistake they are lost now"; which was just fluff because the coins would have never gone anyway. The response was short, aloof, rude, and inaccurate.

Also beware that PayCoinPoker is posting full names and personally identifiable information about it's members...
So if you have an issue with Paycoinpoker, and they don't agree with you - they will respond with aggression and if they have access to your private info, they will post it in forums....I saw this first hand between them and another member this week. Red flag went up.