I just purchased it today. Download the UFC app and then set up a payment option on your XBox. It's for a limited time. Take advantage. No strings attached. No, I don't work for Microsoft and this is not a solicitation for XBox.
My proof of purchase copied and pasted below:
You sent a payment of $31.49 USD to Microsoft Corporation
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|UFC 154 US PPV SD
||$31.49 USD||1||$31.49 USD|
Invoice ID: PI000000ZGYD31Z