When Bay refused to pay, they assaulted him, she said. The brothers also allegedly assaulted three police officers who were called to the set.
The spokeswoman said Bay suffered a minor injury to his face but declined medical treatment. She spoke on customary condition of anonymity.
The two men, aged 27 and 28, were arrested and face charges of blackmail, assault and assaulting police officers.
"Transformers 4: Age of Extinction" is partly set in Hong Kong. It stars Mark Wahlberg and is to be released next June.