Scott loves the Google Nexus IV, but it's GSM only with T-Mobile. He's not much a T-Mobile fan, and would like to move it to another network. Leo says that since it's GSM, it only would be able to work with a carrier that uses GSM, which is AT&T and T-Mobile. Verizon and Sprint use a different technology called CDMA.
Google created the Nexus to be a developer phone, and as such, it may only be designed to work with T-Mobile. So he may just be out of luck there. It's a real shame too, because the Nexus phones are really popular. People really want vanilla Android.