They must have a special sim if one can dynamically switch between T Mobile and Verizon, and , if so, it sounds like this will only work on phones that are carrier agnostic. Sort of like Project Fi, if I'm not misunderstanding this. ???
I wouldn't rely on the accuracy of that article.
I imagine it is one or the other. The website itself makes no mention of running off both simultaneously. I doubt us mobile has the oomph to get verizon to agree to that.
Still it is a nice low cost mvno that will work well with verizon if the pricing stays the same.