The offer is 25,000 "on approval" but you owe them $75 regardless of cancellation, so they could take back the 25k.
"This is a one-time, limited time offer for new cardholders that, in response to this offer, apply and are approved for an Alaska Airlines Platinum MasterCard credit card account. Cardholders that qualify for this offer will get 25,000 Bonus Miles in addition to any Bonus Miles they would otherwise earn under the Alaska Airlines credit cards program terms and conditions. Such Bonus Miles will be credited to a Cardholder' Alaska Airlines Mileage Plan account approximately 8-10 weeks following account approval date. Limit one-time 25,000 Bonus Miles offer (no cash value) per new account. This promotion is offered by BofA Canada Bank and may be amended or cancelled at any time without further notice."
BUT!
"$75.00
Annual fees post to your account if/when the application is approved, whether your card or other credit device is activated or not, and annually thereafter on your anniversary date."