New iPad + T-Mobile's $30 Walmart Plan?

My better half has a 64GB Verizon iPad (3rd generation). He blows through 2GB of data pretty quickly, but it's my understanding that all current iPads are dual-mode CDMA/GSM and are unlocked and can therefore run on a GSM network, provided the frequencies are compatible. I would like to get him setup with the $30 T-Mobile/Wal-Mart service plan, which is "unlimited" data, and unlimited texting and 100 minutes (which won't be needed obviously).

So here's my question: According to Wikipedia, T-Mobile's UMTS/HSPA/HSPA+ network runs on 1700mhz and 2100mhz, with 1900mhz joining the party later in the year. Also according to Wikipedia, the 3rd generation iPad supports 850, 900, 1900, and 2100mhz for UMTS/HSPA/HSPA+/etc. So are both 1700mhz and 2100mhz frequencies required for 3G/faux-G connectivity, leaving him on EDGE until their 1900mhz rollout? Or will the 2100mhz compatibility be enough for him to get 3G speeds?

I guess I should also use this space to confirm that both 3rd generation iPad models are indeed unlocked and able to be used on GSM networks, despite being sold as a "Verizon" product, right?

We've both had very negative experiences with AT&T in the past, but I suppose if there was a comparable data-only plan running on AT&T's network he'd probably be willing to give it another shot, on the basis that the T-Mobile plan wouldn't work or would leave him on EDGE-only speeds.