Guys, Tirico and Dungy work for ESPN/ABC. Sunday Night Football is a property of NBC. My guess is it has something to do with the cancellation of the Ravens/Steelers game but I have never ever seen an announcing team jump networks like this.
Tirico and Dungy work for NBC. They work in the studio every Sunday night and also broadcast the Notre Dame games on NBC. My guess is that Tirico and Dungy did the game last night because Michaels and Collingsworth were going to broadcast the game on Thanksgiving night.
It's possibility that Collinsworth and Michaels always had Pittsburgh-Ravens Thursday and still have it Tuesday.
Dungy didn't swap anything. He's been the pregame show guy on Sunday night on NBC and he and Mike T have done a Sunday night game together as fill in's.