Bullshit antennae are twitching ..
There's an awful lot of noise here, but fuck all real detail.
My first instinct is to note that unless and until the law is changed (and that won't happen anytime soon with Brexit clogging up the schedule) it would be illegal to allow a vehicle on our roads that is not under the DIRECT CONTROL of the driver.
Yes, you can have all the gadgetry in the world. But until that pesky law is changed, it will be a human that takes the fall for anything bad.
That's point #1.
Point #2 is that lorries are subject to specific regulations regarding the time a driver spends driving and resting. Those regulations will still have to be respected, since (point #1) that's the law. And a driver "resting" while the other driver drives is not counting as resting.
What is really happening, is that some lorries, fitted with "self driving" technology are going to be babysat by professionals who (I hope) have a very clear contract with their company.
The fact that the UK press is hysterically reporting this uncritically as some sort of revolution is pathetic, but not unexpected.