With the VZN product, they combine various elements (including that which requires a data plan) to simply get the GPS coordinates. Getting the maps and the routing also requires, as you say, a data plan.

The Verizon situation is a bit unusual in that they combine information send by data with information picked up from GPS satellite to get a “more accurate” location.

Or, maybe, Verizon just claims this.

In any case, for those without a data plan, Garmin’s newest offering (which stores maps locally) might be an option. Note that it won’t work with Verizon phone unless you have an external GPS “puck.”