I spoke to an AS rep and she was adamant that I send the front and back pics. I went ahead and submitted with just the front and got this email in reply:

"Thank you for your interest in our award winning Mileage Plan program. In order to process a Tier Match to our program please send us a copy of your current elite card (front and back)*, a mileage statement showing your current elite status in the other program and your driver’s license or passport.

If your original email did not include all of these documents, please send us a new email with your Alaska Airlines Mileage Plan number and all three documents attached. Once we have received all of these documents allow 2-4 weeks for processing. When your Tier Match is complete, you will receive a welcome email and can check your status online at alaskaair.com/myaccount.

We look forward to welcoming you into our program and flying with you for many years to come!

*Please Note-We only offer Tier Match for the following Airline programs-Air Canada, American Airlines, Delta Airlines, Frontier Airlines, Hawaiian Airlines, Jet Blue, Southwest, United, Us Airways, and Virgin America"