Esso premium is no longer ethanol free. At this point, Canadian Tire premium, Costco premium, and Shell premium are the only ethanol free options. Esso used to be, but about 2 or 3 years ago they started adding ethanol to their premium as well.
Anyhow, FWIW we use Costco premium in our Volt, so we are ethanol free, but due to the vacuum system it's not really a huge issue regardless - what exaserbates phase separation is the exchange of air in and out of the tank as part of the daily heat/cool cycle - cool nights, sunny hot days. Traditional fuel tanks "breathe" in and out and at night humid cool air is drawn into the tank and phase separation occurs....which with fuel left sitting for long periods (which is the main reason you should avoid ethanol fuels in small engines like lawnmowers, snowblowers, weed eaters etc which are traditionally left sitting for long periods with the same fuel) causes phase separation.
For cars that use a lot of fuel regularly it's not really an issue as the fuel doesn't sit long enough to generate any amount of water volume, but for something like a Volt where the same fuel can be in the tank for a year before the computer determines some of all of it MUST be used (a cycled called "Fuel Maintenance Mode") the vacuum system helps eliminate a lot of the issue as the tank doesn't breathe like a traditional cars fuel system.