Thankfully this is the only account of a polaris catching fire that I have heard of or seen so I am confident that this is very rare.
Watching the video I can't help but wonder what would cause this. Reading the comments carefully the poster made it clear he had did not have a custom exhaust extension and from what he typed it looked like the engine was overheating/losing power prior to catching fire.
So what happened? Faulty fuel line? Engine oil leak/low oil? Faulty radiator pump? Too many electrical mods etc....
Also for those gearheads out there do you think there is any danger of running an exhaust pipe down the center to the rear? I assume the temps will not be that hot to start a fire on the underside once you leave the muffler.
There is no clear answer from the OP after 3 years so I assume NDA with polaris or maybe he settled with insurance, walks away and ends the story there.