Keep in mind, that scale is for high-powered games. Pathfinder, for example, uses a very similar CR breakdown for their summon monster scale, allowing things like Gelugons and Glabrezus to be summoned by RAW (not that Pathfinder is wholesale at a higher power level than normal 3.5, but I do believe it tends toward it). But you can't take ANY scale as total gospel truth. Take a look at the d20 SRD's Summon Monster VIII, just for a quick example. The Celestial Dire Bear's CR is 9. The rest of them, respectively, are CR 9, 11, 7, 9, 11, 7, 11, 10, 8, 10, and 9. It tends to be around the 9-10 range, which is how I determined the scale I used, but there are outliers. Look at SM VII, just off the top of my head: babau should be a SM level lower, and the bone devil should be a SM level higher. There are errors, bad judgment calls, et cetera. You just have to keep an eye out for them.
My point is that it's not so easy to create a static scale - in my guide, I did note when the stated CR of a creature was over- or underrated. At best, it's a guideline and a heavily heuristic process. I will say this, though: as long as you ignore any assigned CR in the Monster Manual II and don't allow the summoning of creatures with the dragon type (which, being basically awesome in all respects, is often too powerful for its CR), you'll be 95% okay.