Interestingly enough, one of our hardware guys had another one of these CAT1 with FW 1006, calling itself 'XBee Cellular' and not 'XBee CAT1 VZ'.
So a partial answer is, trying to go from FW 1006 to 100A still fails (as of 2018-jan-11). But going from 1006 to 1008 works, then you want to power off the module, power back up, then go from 1008 to 100A.
Now at this point, the 'long version' command will cause the xbee to claim to be 'ver 100A.2 Prod Build: Nov 21 2017 17:02:57' and it will never get past AI=22, so 'registering'. It cannot connect. So I had to power the xbee off one last time (a 2nd time) and after it powers back up, 'long version' returns 'ver 100A.1 Prod Build: Nov 21 2017 17:02:57', and it will now be able to connect. I have NO CLUE what the 100A.2 -vs- 100A.1 implies, but apparently we don't want 100A.2