Are these paid for by car makers like BYD?
Yes, BYD is paying for several, so are many others. I expect it to be quite a large fleet eventually. Just imagine how many cars and electric/hydrogen smart trucks China will export a year, it might approach a million a month if things continue.
These PCTC seem to be getting bigger and bigger with each order, right now they are around 200m long, but the biggest container ships are 399m.
China will also need to export just huge amounts of agricultural machinery too, and mining.
Brilliant, again, example of civil military fusion, BYD pays for PLAN ships, as all these ships are designed to accommodate the PLANs needs in war time, as I understand it.