The new Verizon iPad includes a micro-SIM card slot to allow users to roam on 3G networks worldwide. But as discovered by a forum member at MacRumors, it also allows owners of the Verizon iPad to use a micro-SIM card to connect to AT&T's 3G network in the U.S.
User "jsnuff1" bought a new iPad Friday and took the AT&T micro-SIM card out of their iPhone 4S. Placing it into the iPad and entering the AT&T APN carrier settings then allowed them to connect to AT&T's 3G data network.
When connected to an AT&T HSDPA network, the iPad will even display that it is connected to a "4G" network, reflecting the change made in the iOS 5.1 software update. However, the Verizon iPad cannot connect to AT&T's 4G LTE network, only its high-speed HSDPA network.
To distinguish between the two, the new iPad shows "LTE" in the upper left corner when it is connected to a true 4G LTE network. AT&T's HSDPA network is capable of speeds similar to 4G, which is why it shows as such.
Apple released two different 4G LTE models of the new iPad to connect to the unique frequencies of the respective networks of AT&T and Verizon. But while those who buy the AT&T 4G LTE iPad will not be able to use it on Verizon's network no matter what, Verizon 4G LTE iPad owners can still switch to AT&T's 3G network if they choose.