Rumors have been flying for a couple of months that Verizon is set to introduce LTE phones with world roaming capabilities any time now. But according to the practical experimentation of one XDA Developers member, the HTC Rezound already has this ability, somewhat hidden. When "i rule 123" disabled the 4G LTE radio on his Resound, he noticed a new option for a Global mode. He popped in a T-Mobile UK SIM card, and lo and behold, it both made and received calls - no hacking required.
Of course, this is XDA we're talking about here. After enlisting the help of his fellow forum-dwellers, the Rezound owner managed to coax the phone into using both upload and download data, and receiving text messages. Unfortunately sending text messages is impossible at the moment, but plenty of folks are actively working on the problem. The international calling and data seems to work fine with home-made ROMs, including the latest AOSP Ice cream Sandwich build. For all of these, all that's required is a few tweaks of the APN settings.
The real question is, was the international functionality included at the behest of HTC or Verizon? HTC's got a clear motive for including it: with some slight modification they can start pumping out Rezound-ish hardware for most world markets. But it's hard to believe that they could sneak a GSM radio onto Verizon's LTE phone without the carrier being aware of it. If that's the case, why hasn't Verizon enabled international roaming? Why wouldn't they want to give their customers more options, not to mention hyping up their own product? The only reason that I can think of is that they're waiting to unveil LTE/international roaming plans that aren't quite ready yet.
This discovery brings Verizon's other recent phones into question - how many of them are hiding a stealthy global mode? I'm fairly certain that the Galaxy Nexus LTE isn't hiding any surprises, but perhaps the DROID RAZR/DROID RAZR MAXX or LG Spectrum are. There's not much I can do to test our review unit from North Texas, but we'll be keeping a lookout for similar news for other models.