I don't specifically know the regs, but did go through the NGC website after I posted this and did find links to forms required as part of chip and token destruction:
https://gaming.nv.gov/modules/showdocument.aspx?documentid=2286
https://gaming.nv.gov/modules/showdocument.aspx?documentid=14868
Combined with the fact we know Paulson provides chip destruction services, we don't see even single cancelled chips available as souvenirs in a gift shop and Jim at the Chiproom can't get his hands on them for resale, it's safe to say that if it's not in the regs specifically, pretty much every casino in Vegas shreds their chips when removed from circulation.
My revised statement is, "The NGC probably recommends accommodates all chips be destroyed when removed from circulation."