The white Cadillac has blue plates. Assuming the "CCC" positions the vehicle in China, it has to be on the mainland and not in Hong Kong. Hong Kong license plates are yellow. Mainland Chinese plates are blue. If crossing from the mainland to Hong Kong you must have both plates. "Cross-boundary vehicles are regulated under a quota system jointly administered by the governments of Hong Kong and Guangdong. Quota holders are required to apply for two documents – the international circulation permit and the closed road permit – before driving into the city."

Ref: https:// www.google.com/amp/m.scmp.com/news/hong-kong/law-crime/article/2026353/mystery-black-shanghai-audi-prowling-streets-hong-kong%3Famp%3D1