Okay, I have done some armchair detective work on the cold case of the sessions and the reference discs for Easy Tiger.
Currently, there are two known: “Rat Classics Vol II” or RAT2 (https://www.discogs.com/release/11307855-Ryan-Adams-Rat-Classics-Vol-II) and “Color Bars” (https://www.reddit.com/r/ryanadams/comments/oy3jtb/anything_but_no/). After some prancing around in circles and talking to myself, my hypothesis now is that there are at least two more similar reference discs.
Vital in this context is that it has been stated in interviews that the Cardinals recorded 60+ songs during the ET sessions (http://mega-superior-gold.blogspot.com/2013/02/easy-tiger.html). If you do the maths in relation to what is, on the one hand, on the tracklistings of RAT2 and Color Bars (about 30 songs) and, on the other, Easy Tiger and III/IV (where the songs ended up - about 40 songs, including bonus tracks) there are about 20 officially released tracks “missing” from the two known reference discs (RAT2 and CB). And 20 tracks are most likely too much to fit on a reference disc of roughly the same size as RAT2 and Color Bars.
If we suppose that there are, in fact, two more reference discs the numbers do seem to add up – together they would contain the other 20 officially released tracks and something like 10 more “unknowns” (the equivalents to “Party Clown”, “People Make Mistakes”, etc.). Then each disc would have about the same proportions when it comes to known and unknown tracks as RAT2 and CB (about 10 that appears on either ET or III/IV and about 5 more unknowns).
Back on the old forum, there was a dude who claimed to have had RAT1 but that the disc was too damaged to play. If that was true, then there is also at least another disc titled Rat Classics (Vol I). Then it would follow that there is also a RAT3, Color Bars 2 or something like that.
Anyone have any qualified intel on this or perspectives that weaken my hypothesis? Basically, the reason that this issue haunts me, is that neither “Arkham Asylum” or “Trouble on Wheels” (which I love to pieces) have appeared in studio versions and judging by their live debuts (September–October 2006), it seems likely that they were recorded during the ET sessions.