Yes it has to do with CDMA network. Not sure if anyone that is using the Verizon unlocked model on gsm network and has data and talk at same time.
Actually I won't be using it on a CDMA network at all. So I would like to know if the CDMA version allows data and talk at the same time on a GSM network?
Yes if you are on a GSM network it will work.
I frequently talk and surf simultaneously on my Verizon iPhone 5. You just have to forego the telcos' antiquated voice services and use one of these apps:
Skype
iGVoice
GV Phone
TextPlus
etc
All have quite good voice quality over wifi or LTE.
No it's more that I want to be able to check email or other data depending services while on a voice call.
Not sure I follow you, unless you are saying you want to be able to press Apple's preloaded cute button for voice calls rather than install another. You still talk to people all the same, except the other apps let you put voice in the background and check email etc.
As other posters say though, if you are on a gsm network with 3G yes Apple's voice app allows simultaneous use too.
Yes if you are on a GSM network it will work.
So the LTE transceiver in a VZW iPhone 5 can use a GSM/GPRS/EDGE network? I didn't realize that it's that backward-compatible. I assumed that when LTE isn't available, it drops to CDMA. Is that not the case?
No, it uses Verizon's network in the us so it can't bounce to GSM it's carrier locked but its a world phone so overseas it can bounce to CDMA or GSM etc