It looks like UL325 is voluntary in most areas so you would have to check your local codes. I found this in a NACHI document that I have on my hard drive.
January 1st 1993: All residential doors required to have “secondary entrapment protection”
electric eyes to sense anyone passing under the door while it is moving.
There is no code reference in the document so I do not know where it came from.
I prefer to err on the side of caution and recommend that sensors be installed if not present. It is a relatively cheap fix and could save a child's life. It's kind of like GFCI's in a 1060's home. They were not required when the house was built but should be added for safety.