[IKE]

While CVTs are often use in industrial equipment with Fixed speed AC motors, you don't often see them in EV aplications because an Electric vehicle motor has the properties that a CVT typically has. Usually with a 2-3 speed transmission you can get all the performance and efficiency you want/need. Also, CVTs are are typically a double edged sword on the whole efficiency thing. Almost all use a cone, ball, or belt and sheave system that invariably has a little bit of conflicting friction at the contact patch. This friction tend to make CVTs have a lower prowerr transmission efficiency. Where they do a lot of good though is with motors that have a very narrow band efficiancy range (think A/C motors, or some genertator or governed engines). On these applications the CVT can vary output speed while the motor stays in it most efficient or powerful state.
I am a huge fan of CVTs and even designed a new one while in college. If you want a great CVT design resource check out:
"Traction Drives: Selection and Application [Hardcover]
By Frederick W., III and Shube, Eugene E. Heilich"
This is a great book that devotes 50% to fixed ratio traction drives (think gear systems without teeth), and 50% to all metal CVTs (sorry no rubber belt system).