So I brought one Pro1x with 2.1.5 GMS-less, and one stock 2.1.2 Pro 1x, to the Cayman Islands, using a new Flow sim card in each one. Flow operates both LTE and GSM network service.
After extensive trial and error, I am sorry to have to confirm that the only way to get voice service with these phones on Flow is to lock out LTE and select "GSM only".
Allowing the phones to connect via LTE showed good signal strength, and SMS and data worked, but voice calls were unable to connect about 90% of the time. On the odd time that LTE would connect, the quality of the voice call was much bett