Most (if not all) CDMA carriers will only activate their own devices anyway.
I.e. Sprint won't activate a Verizon device and Verizon won't activate a Sprint device.
However, i believe that yes, you could switch verizon to GSM carrier, and then back to verizon.
"That's it then. Cancel the kitchen scraps for lepers and orphans, no more merciful beheadings... and call off Christmas."