Hi Chikitin,
Yes, the data transfer between Studio One 4 and Notion 6 is bidirectional, but only through internal file transferring system, but it’s not Real-Time synchronized. After doing any changes, you have to press Send To Notion or Send To Studio One. I did some tests with the previous version of Notion 6.5 and Studio One 4.5… Definitely it’s better than nothing, but still far from the real meaning of integration between two apps.
We need Bidirectional Real-Time synced integration, with option Refresh the project when one of the apps wasn’t active and then came online, without the need of creating new projects, and when you add notes, or dynamics, or expression, or if you do any changes to the mixer, velocity or CC in Dorico, they should appear immediately in Cubase, and vice versa.
This would be real time saver… and will be very welcomed by those composers who prefer to work with notation, because they would be able to use Dorico instead of Score Editor. At the end the project will be in both apps and on the score sheet. 
Just like killing 3 rabbits with a single bullet.
Celemony by creating ARA 2 technology showed to the World that this is possible for audio editing. For MIDI, Automation, Inserts, Sends, Comments/Track Notes should be even a bit easier task to be achieved, since MIDI synchronization already exists…
Best wishes,
Thurisaz