Treadmill Hiit Yes !
I do HIIT on treadmill all the time; machines go FASTER than 15 mph !! I've gone only up to 14.8 mph.
You can learn to control the adjustments at fast speeds. However, it is okay to momentarily step on the sides of the machine, straddle it, to bring the speed back down to recovery pace. I do this all the time. At end of sprint, step feet off to side and change speed, then get back on.
OR, when I'm done with a sprint, I just get off the machine and walk around for part of the recovery, then get back on and slow it down for the remainder of the recovery.
DO NOT HOLD ONTO THE MACHINE WHILE SPRINTING. THIS IS CHEATING BIG-TIME.