I think the thing about the Maag EQ is that the fixed bands are set such that they have a very noticeable effect on the sound of many instruments, for example, cutting 650 makes guitars sound clearer and less boxy. Plus, the bands have a VERY wide Q, so a lot of audio is being boosted or cut when twisting the knobs. The high shelves reach way down below their stated frequencies -- the 2.5 shelf actually starts boosting at around 400 or so. Put these characteristics together, along with perhaps a little modeled saturation, and you get a very "musical" and popular EQ.
Cheers,
Eddie