It appears that Apple may have decided to not restrict the AT&T SIM card operations over other networks for the New iPad 3 as there is now confirmation that a Verizon iPad 3 which supports 4G LTE can also work on AT&T’s 3G data network. This is accomplished by simply inserting an AT&T SIM card into the Verizon iPad.
Verizon LTE New iPad 3 works on AT&T 3G as well
The details were found by early buyers who reported it to MacRumors which later confirmed it. The same test was carried out by Mashable testers and came up with similar results.
Simultaneously, a micro-SIM card from an iPhone 4S running on AT&T can also be inserted into a New iPad 3 from Verizon, replacing the existing SIM card. You will need to tweak a couple of the iPad’s carrier settings to support AT&T but that is about it.
This comes in handy if you happen to own an AT&T smartphone with a 3G data plan just in case you find yourself wondering outside of Verizon’s data coverage area with your New iPad 3.