Subscribe to tags from different vocabularies / select by list instead of autocomplete

I have 2 vocavbularies with exactly the same terms, "Forums" and "Standards" (due to the fact that using the Forums terms as terms messes up things completely)

In admin/messaging/notifications/content, Tag subscription, I selected my 2 vocabularies.

In user/x/notifications/add/taxonomy, there is an autocomplete box which reaches only one set of terms without refering to the vocabulary it is memebr of.
When I select a term, Notification works only for Forums, meaning it took only the terms of the first vocabulary.

1) Is notification working with multiple vocabularies?
If not, this is will be change in a feature request (and a bug as the GUI aloows to select several vocabularies)

2) If yes, that would mean :
2a) that Notifications merges all terms from all selected vocabularies in a single list, which is non-sense as the same term may exist in different vocabularies (as in my case) - this would be a bug
2b) there is trick I am not aware of - please explain

3) Is there a way to change the term selection widget? I hate the apperently popular Autocomplete checkbox because one has to guess which terms exist or to try the 26 letters of the alphabet

Thanks for help