I am certain that Disney has control of the canons.
Agreed.
It's interesting to note that there is very little (virtually none) "wetness" on Splash Mtn. without the water that's "pumped-in" and "cannoned" or sprayed onto guests.
Contrary to common knowledge the "splashes" on
Splash Mountain are overwhelmingly NOT caused by the
logs hitting the water in the troughs (a very few
small ones are.)
The heavy drenching water effects (including the BIG
one at the bottom of the final drop) are actually
"sprayed" and/or "launched" at guests by adjustable
water pumps and/or water cannons.
Disney actually holds a patent on the Splash Mtn. "logs" that is specifically for a vehicle that does NOT splash much water.
The first spot that can drench guests is right after you have exited the first lift-hill following boarding.
As you watch other logs travel down the "final big drop", at that log's "splash-down," a large water-cannon can shoot gallons of water over onto YOUR log. The CM's will usually shut off that cannon in cold weather (but not always.)
There is that one spot after the first internal drop that can cause some back-splash into the log, but most of the rest of the wetness is due to intentional (and controllable) "pumping."
Even the "big finale's" water comes from electric water misters inside the tunnel after the big drop.
Sometimes the waterfall in the area where you are held just prior to the "Zip a Dee Do Dah" boat will splatter the right-side guests pretty good, too.
But that is also controlled.