We have them in Ontario and the plate is attached to two plastic anchor thingys behind the front bumper.
I was suspicious my self that they will not last, but seem to be holding up fine.
If they strip out, I will put a strip of metal as a backing plate then use stainless hardware and some nylock nuts to eliminate the issue.
I added a plastic cover since the plate is held with just two screws at the top and the plate bent up on the hwy.
'00 XJ - Somewhat modified
'01 Venture - high mileage, paid for, shut it