In that context, the Volt (and other hybrids, plug-in or not) would either be banned or be required to disable their ICE engines in the city.
But EVs are really not perfect anyway.
People say why have two powerplants. The reason is to get rid of the (environmental impact of) 300 mile batteries.
90% of the time, 10% of the battery is enough.
From the page above:
"If you never miss a plane, you're spending too much time at the airport."
I feel that the obsession with pure electric has crippled the fight against pollution and CO2 emissions. Every car with 20 miles of battery range is probably a lot more impactful in the fight against climate change than 10% of cars with 200 miles of battery range, and has fewer major tradeoffs (cheaper, limited range/recharging is not an issue, much less need to build an entirely new charging infrastructure).