I have never seen a CDMA handset not provide GPS info to the PSAP as long as it was not in a bad position for a fix, including iPhones on the metroPCS and Sprint networks. I have no experience testing on Verizon. I was always advised from the beginning of the phase 1 hi res location rollout that the 911 location function was not able to be defeated in the handset through normal means. Considering the gyrations the carriers have to go through to insure proper configuration and continual verification of the 911 location system it wouldn't make sense, IMO, to allow handsets on the network that allow you to disable location on the system. It's kind of a big deal to carriers when a PSAP can't obtain location info from the handset in a 911 call, and if they get a few of them the places near me are usually initiating troubleshooting with the carrier and location service vendor.

There may be some handsets somewhere I have not seen that let you turn it off.