You can track Ionity‘s progress here: https://ionity.evapi.de/#/

I have no doubt that they are serious and ambitious, but they are so far behind Tesla that it‘s not likely that they will catch up until 2020. Also, they are planning to place their fast chargers only 120 Km apart to accommodate for a wider range of vehicles, which puts them at a disadvantage too.

350kW is about 1800 m^2 of PV panels; you need twice that plus a battery bank to operate at night. You might want a grid tie only so you can do net metering. At current prices for Chinese panels (not counting the Trump tariff) that's on the order of a million dollars. Now double that to pay for the electronic chargers themselves. So $2 million in capital costs and no recurring costs except maintenance. That's almost certainly cheaper to build and permit and operate than a petrol station, and those seem to pop up everywhere.

I don't think it will take more than a couple of years for well-maintained superchargers to be ubiquitous, and that's if you give away the power for free with government subsidies. If you charge customers for the energy, it might happen even faster.

> 350kW is about 1800 m^2 of PV panels;

Or about 1/7th of a windmill.

Windmills require good locations to be cost effective, solar works almost anywhere.