I have not used LiveTrack, but I know that Verizon service is spotty along Barr Trail.
We use their cards for the timing gear. Some locations are ok. Others like Barr Camp require an external antenna placed in a certain location. Above treeline I've had fewer issues with voice calls but the data service may or may not work as you are on the edge of what it can deal with. Once at the summit, the second you step away from the east face the signal is usually lost.
Either way, we expect a full report on Aug 18th. :-)