lip synching
I watched half of this, and there is NO WAY this was live singing, especially from overweight people who are thrusting their hips back and forth, jumping around and kicking. Never once did I hear even the slightest change in the voices as they're shaking their collective booties.
It was especially evident during the "Good Morning, Baltimore" number. Tracy, running across the street, jumping on sidewalks, doing the Mashed Potato, all the while singing like she's standing in her shower. Come on.
And the "Nicest Kids in Town" number was also lip synched to death. With all that motion, those people weren't even breathless for the slightest of seconds.
I'd say this could conceivably be considered Hairspray Live, since it's supposedly being beamed into our living rooms as it's happening. But they NEVER claimed, in any PR material that I've read, that the vocals would be sung live on camera.
Given that, it's definitely a cheat!