I don't know what "SOT" means, but in answer to the question, NO, Calif. Police Depts do NOT buy Class III weapons and hand them out to the film companies.
Special Occupational Taxpayer, it's what you'd be if you made Booze that you wanted to sell or MGs and class III weapons for the most part, their are different levels of course but I'm pretty sure you have to have one present with the rented MGs and DDs at all times to be legal, also I'm pretty sure that according to the BATFE website that renting guns to movies is not a legitimate reason to become a dealer or renter of post 86' MGs, so to do such business one would also have to cater to LE or military on a regular basis or lose the license. In Canada though if you are a museum or a rental agency that deals with the motion picture companies you can have pretty much whatever you want, I don't ever recall seeing anything mentioned in US law about movies.
here's some reading
http://www.recguns.com/Sources/IIF1.html