What struck me as odd is that it's not going very far - less than 150 km on the map. And if London is the main target for onward distribution of containers, it's still 40 km from London Gateway - a reduction from the 120 km for Southampton, but hardly worth it at the cost of an extra transshipment. 

For wider area on the south and west of London it doesn't really help, though for the north and east it does avoid wider greater London. But I'm sure containers are loaded onto these trains according to their final destination and the exact route planned for them, so it should make sense.

Assuming that it replaces existing truck flows then indeed, it should free up HGV drivers.

Of course new rail freight flows will need drivers, for which there's a relatively limited pool.

I'd suggest that HGV and PSV drivers are probably not interchangeable.

In a similar vein it occurred to me this week after seeing very full trains in Bristol due to bus cancellations and unreliability that although we think of road capacity as the main constraint on transport, perhaps we ought to think of driver labour, which skews towards trains and trams. .