When I talked to the rep at Union she said to stop by one of their stores and try out a sim and see if it worked in my phone......So I did just that and it did indeed work. I did not try data, but it looked like data worked as well as my phone updated my Microsoft outlook while we were testing it.
I am running CM 10.2.1 on this DINC 4G LTE and it does look like it will work great as a GSM option. Whether I chose to use it here in Wyoming or need a GSM phone in a foreign country.
For a phone that receives such little love and was forgotten by HTC.....it really is a very solid unit.