Actual CAT M1 Coverage in the USA
Verizon and AT&T both say that they have nationwide 4GLTE CAT M1 coverage in the USA, and later this year T-Mobile will add nationwide NB-IOT coverage (and later CAT M1 coverage). All 3 carriers have also said that it is just a software upgrade to existing 4GLTe towers to add CAT M1 (and NB-IOT) coverage.
However does that really mean they have actually upgraded all of their (and their partner carriers') 4GLTE towers to CAT M1, and that there are no holes in their nationwide coverage today? In other words, can I look at their various 4GLTE coverage maps and know that we will actually have CAT M1 everywhere that 4GLTE is??? Why don't they publish CAT M1 coverage maps, or at least put a notation on their 4GLTE maps that says "CAT M1 coverage is/isn't available in all 4GLTE locations on this map"?
In the past, cellmodems had fallback coverage to lower speeds just in case the cell tower in that area had not been upgraded to the latest technology. However, with the newer CAT M1/NB-IOT modules (including the Pycom GPy), that is not the case --- the only fallback is CAT M1 to NB-IOT, and vice versa --- not CAT M1 (or NB-IOT) to 3G or 2G.