We have good news for you all, we have found out that the New iPad Verizon 4G model is cross compatible with At&t. You will be able to insert a AT&T Sim card in your Verizon without any problem. A user from the Macrumor forums was able to verify this, and we have have video proof below.
The only bad news is the fact that the Verizon iPad doesn’t support AT&T’s LTE bands. You will be able to use 3G from At&t on your Verizon iPad, but not 4g. This could come useful in area’s where Verizons LTE network isn’t as strong. All you have to do is pop out the SIM card from your AT&T phone and put it right in your iPad.
The Big question on everyone’s mind buying the Verizon iPad was whether data from AT&Ts 3G network would work on this iPad, or if Verizon/Apple would block this.
I was one of the first to obtain a Verizon iPad and can happily confirm that this is allowed! I used my ATT iPhone 4S sim card and took out the Verizon sim, and data worked! You must apply the AT&T APN carrier settings before this works though.
Will this come useful to you?