I don't know if that would work as I imagine that kind of paint is probably quite thick and will be harden when it sets. The PVC roofing will be quite flexible and is prone to shrinking and enlarging with heat which might crack the paint.
The roofs probably lastest longer than expected and they should be cheap and easy to replace.
The reason they probably went with this concept is because it's easy to print on, it can be easily stretched to fit most shapes and it works. It also has the added benefit of being able to print on both sides so the inside of the buildings will show off the print.
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I must have found this interesting enough to take a photo on my last trip. If you look closely, you can see how the multiple panels are heat welded together and how the panels are attached to the skeleton of the roof.