It appears there is a Qualcomm part in the Verizon & Sprint models, but its not the SoC, those will be Exynos for sure.
Samsung pushes out Qualcomm for Galaxy S6 on AT&T's network | UTSanDiego.com
“While we still expect the Verizon and Sprint Galaxy S6 versions to sport Qualcomm modems – both build on legacy CDMA networks – we believe this change signals Samsung’s clear intent to utilize propriety baseband whenever and wherever possible,” said Rolland in a research note.
Given the legacy CDMA that those carriers need support for Samsung may not have that in their modem bag of tricks.