This post on the Drum-Tec site cracks the door open on the "hot spot" topic.
"The "hot-spot" was greatly reduced thanks to the new signal-processing even with analog pads."
I wonder how they achieved that, but it sounds promising.
They also say that the PD-140DS uses two piezos, and a number of electrostatic elements that detect touch.
"In addition to the conventional trigger setup consisting of piezoelectric cushion and rim sensors, the new Roland V-Drum Digital Pads feature electrostatic elements on the playing surface and shell to get an even more accurate signal. In total the signal is being sampled by two piezoelectric triggers and six sensors which make the playing surface sensitive to touch."
This suggests the PD-140 has a similar piezo configuration, but with added sensors for touch sensitivity which allows for automatic switching for rim shot detection and perhaps positional sensing. This is just a semi-educated guess, but it seems to add up.