The Droid xyboard definitely has both cdma and gsm radios, this has been confirmed by Motorola countless times.
So, I went ahead and grabbed my wife's at&t micro Sim from her iPhone and plugged it into my xyboard (i'm not rooted). First it rebooted, as it always does when a new Sim card is inserted, then it told me, Sim card from unknown source, I switched the network mode to gsm/umts, and it detected that it was an at&t Sim as all the at&t access points were automatically listed, but it still would not work, there were no bars listed even.
This leads me to believe that its definitely Sim locked by Verizon and would probably require a code from them to carrier unlock!
Sent from my Motorola Atrix 2 with AT&T 4G