The regs say words to the effect " chips will be disposed of in a manner approved, by the chairman."

If you call and ask, they will tell you to grind them up. Sorta like "don't ask-don't tell"

A casino that is going out of business does not have much to fear.
A casino issuing a new rack does not want the chips to turn up at other NV casinos where they could be accepted for table play.
So, most are destroyed.