Tyll's measurements on IF are with ANC enabled unless otherwise stated afaik. Beats Studio and Bose QC15 will further not operate with ANC off.
More complete datasheets from IF (from the ANC shootout):
The lack of LF isolation on the Studio indicates bad ANC performance (my understanding is that ANC will primarily act upon frequencies below 1khz, and frequencies over 1khz will be handled by passive isolation). Tyll also specifically admonished the ANC performance on the Studio (in the big shootout review) as "pretty poor." They're yet another headphone that has ANC (someone previously mentioned that Beats has done a great job of making "ANC" a buzzword for new headphone shoppers) as a "feature" despite it not actually delivering - likely because they half-assed it (like they half-assed everything else about the Beats).
I remember reading about ANC a while ago, and finding a comment along the lines of "to truly innovate in the field of ANC, requires monumental engineering resources and talent" - Bose spends quite a lot of money and time to make the QC headphones work the way they do. And there's a lot of imitators that basically just rig up an LED on a switch (at least in terms of the end-result).
For comparison, here's an example of a decent passively isolating headphone: