Well in Michigan if we freeze that has to be written up in our SOP's and all equipment used has to be NSF labeled. We need to document how we cool, how we thaw and reheat. You can only reheat in your trailer or vending approved setup. So in fact we are licensed to thaw and reheat.
I put pulled pork and shopped brisket in a half pan and cover with proper lid and freeze that way. Then I thaw in the commercail fridge and heat in the FE100's. To chill I either use large coolers with ice or put 3 or 4 half pans in the freezer at a time.
FYI a solid lump of frozen butt will take a lot more than 30 minutes in boiling water. Actually I'd be surprised if the water keeps boiling. I'd for sure have it thawed before reheating.
I'm not an expert on Canadian vending laws but I'd PM DivaQ and ask her some questions before doing much.
Retired competition cook. BBQ mentor.