Not surprising at all. This was a concern that was raised over a decade ago, even in discussions here on /.
The fact is that road maintenance needs to be paid, and it was long thought that charging taxes on gasoline was a good way to fund roads because it was simple to implement, it scales with how far you drive, and it also scales with the size of your vehicle (larger vehicles do more damage to the roads). So it was relatively fair. It also didn't require invasive data collection, such as how far or where you drove your vehicle.
When it was first discussed here on /., the consensus opinion was that if you drove an EV, you should have a GPS tracker installed in your car that measured how far you drove. We used to have big discussions here about privacy, and the privacy advocates thought that a government mandated GPS tracking you everywhere you went would be an overreach by government. I was generally in favour of paying the fee when you renewed your license plate for the year, where you have to submit your vehicle mileage anyway.
Of course now we voluntarily GPS track ourselves and send the data to our corporate overlords, so that all seems like a moot point.
Will this new law also apply to those crazy guys that power their diesel cars off used french fry grease they get from restaurants?
The free ride for EVs was going to end at some point. If your only reason to get an EV was to evade a small amount of taxation, well you're SOL and should probably re-evaluate your priorities.
In the UK, you have a yearly car inspection called an MOT that registers your mileage at the point of inspection. In that way it's easy to determine what the per mile tax would be. Personally I'd rather a blanket tax on all EVs as it would be easier to administer but I don't have an EV.
However I feel that we're about to discover the hard way the dangers and downsides of the extreme amount of computerisation in modern cars. They're already sending telemetry to the manufacturer, often without the knowledge of the owner, what is to stop the cars from sending similar telemetry to the government? Your car becomes the snitch, especially if people start to fiddle with the mileage before an MOT. There's no need for a new GPS spying system to be installed, it's already there.
BTW, when it comes to diesel, modern cars can't really run off of chip fat from the local chippy and converting it to biodiesel would be more expensive than buying diesel (especially as it won't scale)... however something similar has already been a thing in the UK for ages as we have "red" diesel... which is diesel sold tax free for non-road use (industrial, mining, agricultural, generators and the like, vehicles and applications that would never use the road) with a red dye added for easy identification. A few people used red diesel for road going vehicles but it's never been such a significant issue that anything beyond token enforcement has been necessary.