Hm, did I just light the bulb??
I found an answer it seems. I'll take the above example where a tag's name was 2010 event. Now if I rename it to _2010 _event it changes everything! Now when I search for event it returns results from notes and titles only, and if I search for _event it returns results from tags only - even if this word is in the middle of a tag! And I don't even have to use the "tag:" function anymore! And theres is unprobable that there will be a note that has a word event with _ before it.
I hope this "hack" won't be "fixed" in the coming releases
One more thing. After rename of tags I had to refresh indexing database (or something like that) since it ignored the changes. So I selected all notes, tagged them with a tag test123 and then removed this same tag. This somehow refreshed Evenotes's index and it works!
It seems to work if I use _ but not with . (a dot) . Didn't try other characters.
UPDATE3 (this is starting to be a tutorial it seems)
You can even optimize your tags with word you want to search for and the ones you don't want to search for. Example: Let's say you have a tag "_el _camino _de _santiago". But if you don't want to search all these words, just remove the spaces between them and the tag should be "_el_camino_de_santiago". Hope it makes sense - someone give a better example if needed:)
Ok, I found some other symbols that work aswell: ß and ł or Ł (both are the same in EN). Crazy stuff:)