Some subtle differences with the product offering in the UK (well - it's London only unless you want a van).
I don't see it as competing with the mainstream operation - it's trying to tap into a different market. Presumably Hertz will have competitive advantage over streetcar/zipcar on things like fleet purchase power (though it won't make much difference on the tiny number of electric vehicles they have so far!)
UK scheme is:
•Free Membership, no enrolment or annual fees
•Rent by the hour or the day
•24/7/365 vehicle access
•Full Insurance cover included
•30 miles of fuel per day (cars) or 20 miles per day (vans) included
•Low Co2 cars and vans
•Electric vehicles
•24/7 In-vehicle Member Care