This is how researchers were able to remotely hack several Chrysler models. They used a Sprint hotspot to get an IP on the cell network and were able to connect to any other Sprint device. The cellular modems on these cars were on Sprint so they just had to be on the same network. I wonder if Verizon intentionally blocks this.
https://www.kaspersky.com/blog/blackhat-jeep-cherokee-hack-e...