There was a break for a while if you bought an "eco-efficient" car and traded in an older, less efficient car to be sent to be crushed. I believe that particular deal has ended, but some dealers are giving their own deals or cash back arrangements. It pays to ask the dealer, at least.
When you buy a new vehicle in France it is subject to a one-off tax called 'Taux d'émission de CO2'. This is calculated by the amount of CO2 the vehicle produces against a scale of 7 charges. I assume electric cars do not emit any CO2 so they will not have to pay this tax.