Usually the Muppeteers have little video monitors down below the puppets to see a wide shot of what their Muppet looks like from the audience's view. I'm guessing they don't have this luxury in this parade, unless they have cameras mounted on the front of the car.
They probably also have VERY limited vision from their hidden locations, which means they can't really see what the audience looks like. This means they can only perform very generic and repetitive movements - and occasionally operate the mouth to sync with the soundtrack voiceovers.
I just love the fact that they've put REAL Muppet puppets into the parade. The "furry friend" versions were awkward.