It really only take a few minutes to pull the seat.... and then maybe 4 10mm bolts to pull off the actual mount/track from the the bottom of the seat in the G8. I really don't think it would take that much for you to pull a seat and at least measure out the mounts to see if they're close.
My bet is that the tracks are similar, but not nearly close enough to just swap the brackets and call it a day. But I also think you could get a little creative and come up with a solution over the weekend so long as they're not significantly wider seats. IF the CTS seat is made in a similar way (I suspect it is), you could get both the track and bottom mount off both seats and fabricate a plate to make them swappable.
Would love to see pics if you do it... and I also have (2) spare G8 front leather power heated seats taken totally apart in my basement. I could send you a few pictures if it helps, but shoot me a PM.