I'm continuing my own research as I wait for responses from the awesome BGG community.
Here's what I've found to support the idea that the iPhone from Straight Talk will be a CDMA phone and will be supported by a Verizon CDMA network:
Does Straight Talk Have the Same Coverage as Verizon?
iPhone 5 Straight Talk: 7 Facts to Know Before Buying
That last link is directly off of Straight Talk's website FAQ. Scroll to the bottom where it says the following:
Does my iPhone use a SIM card?
No. Although your Straight Talk iPhone may contain a SIM slot, DO NOT insert a SIM card into it. Your Straight Talk iPhone works on a CDMA network; inserting a SIM card could alter your settings and stop it from working properly. Please note this does not apply if you are using an unlocked iPhone with our Bring your own phone SIM card program.