Dustin,
I don't know the exact plans for the Loop's motive power, but do know that ex-IRCA 2-8-0 #40 will the primary locomotive used this season, in addition to shay #12. Both #40 and #12 are ready to run now, and I believe #14 is in reserve.
Of course, if this ends up being the final season, I'm sure that they will be running all three locomotives during the course of the season.
If you are planning to fly out on a weekend, you may get to see two locomotives under steam, as the shop crew has been preparing equipment to make up a second section (second train) to run on weekends.
Perhaps Skip or someone else from GLRR could elaborate on this.
Shane