They're starting on the first line. Haula and Koivu have both played with Pookie in international competition, and since Pookie did not go through training camp with them, they're the best chance at having some chemistry with him.
Boudreau will be able to best see what Pookie can do and go from there. It's not a line that will stay over the course of the season. They're predicting Staal will center the first line, Koivu the second, and Haula the third.
Haula has started to get noticed. He was Press Box Boy quite a few times last year, but he is improving. If they move him permanently to a wing, I'll be surprised, and with Koivu's faceoff abilities, they're not moving him off center.
I would wager that Pookie ends up on the 3rd line with Haula unless Pominville continues to be less than stellar, in which case he may move up to 2nd line. Coyle will be first line unless something bad happens to him or he slumps badly.