Often they choose opening acts after tickets have been on sale for a while. If they sell slow they may get the sales move faster by adding a 2nd great act. Moncton is a real happening. AC/DC in Germany 2003 is another great example. And the special warm-up acts like Zucchero in Imst 1999 to please fans from Italy, and Rowwen Heze in Landgraaf Netherlands same year other typical examples. Chicago is sold out so they might pick any act. Still I am impressed by the many warm-up acts they bring on, many that might sell our larger venues on their own.
What about Madison Square Garden? Any good guesses? I loved seeing Ryan Adams in January 2003! He's good. Will there be guest artists this time too? Like in NY in 2003 when Sheryl Crow and Hubert Sumlin came on stage? That was a great bonus!