Out of more than 100 contests, we've only been checked twice. One time we had the 5LB ABC on us and the second time we had to go buy one. The problem is that in small town, 4 or 5 teams hit the hardware store and they are out. One secret (fire marshall's and department personnel stop reading here) is to borrow a unit that has already been inspected from another team. We were at a contest once where the same extinguisher must have been passed to 20+ teams.
I've also had to go buy 1/4" fire screen to put over the exhaust of my pit before too. Like the vigilante health departments in some communities, the FD stuff can get ridiculous. Has there ever been an uncontrollable fire or a fire related injury that would have been prevented with a fire extinguisher at a BBQ contest? Don't get me wrong, I've seen lots of fires at contests but never seen an extinguisher requirement save the day. And I'm certainly not opposed to prudent fire safety, just the fire nazis.