Yes, they're live, and the dressers/make up people that work on the telecast are incredible.
The best example is the year Kristin Chenoweth was nominated (and won) for YOU'RE A GOOD MAN, CHARLIE BROWN.
She had to give her performance in her Sally Brown costume and wig, and immediately following the performance was the announcement of her category.
Her name was called as the winner and she came out from backstage and made a comment at the start of her speech about how that was the quickest change she had made in her life.
"Winning a Tony this year is like winning Best Attendance in third grade: no one will care but the winner and their mom."
-Kad
"I have also met him in person, and I find him to be quite funny actually. Arrogant and often misinformed, but still funny."
-bjh2114 (on Michael Riedel)