Quick update. Just checked
https://egov.uscis.gov/casestatus/landing.do and got this message:
"On February 5, 2015, the Post Office picked up mail containing your new card for Receipt Number IOEXXXXXXXXXX. We mailed your card to the address you gave us. The tracking number assigned is XXXXXXXXXXXXXXXXXXXXXXXX. You can use your tracking number at USPS website the Quick Tools Tracking section. If you did not receive the card, please go to
www.uscis.gov/e-request to request that we resend the card to you. If you move, go to
www.uscis.gov/addresschange to give us your new mailing address."
So they do provide the tracking number and my wife's card will be delivered today