First a premise: I still play SR3 and do not have the money to start SR4.
So, After reading SoE and SotA64 I would like to let my players play in Europe or at least use European elements like the various schools.
Since all my mages are American it is easy to think about them as al renewed hermetics....but now they will meet various other schools and this means that I have to use the rules for hermetic schools.
In MiS it is said that one has +/- for using/not using the stuff of its school....does it means that if I use this rule there will be always a malus or a bonus?If this is the case my hermetic characters using formulas. etc... will always have a bonus or malus since all formulas, etc.. are written according to a school's paradigms? So never without bonus/malus? No more "generic" stuff?

If you read SOTA 64 carefully, you will know that the UMTs do not have bonuses or penalties. However, if you insist on Renewed Hermetism, unfortunately there would be a +/- unless you rule that certain schools are different enough not to give a penalty but not familiar enough for the bonus (but you as the GM has got to think about which schools are far/close to which school).

Most of the stuff under Classical Hermeticism is compatible with Renewed Hermeticism, since Renewed Hermeticism started out as Classical Hermeticism. In general, if it deals with the four elements or psychic templating and archetypes (Jungian psychology and such), then it is compatible with Renewed Hermeticism. If it involves things that differ in philosophy, then you apply the penalty.

Of course, your characters can also browse the stores for material of their school. It may not be very important in Europe, but that doesn't mean you can't find a store packing the stuff you want.