I tried to go through the code in your GitHub repository, but could not completely figure out the behavior...
I am adding new Posts 2 Posts connections programmatically, as nicely documented by scribu. Unfortunately, a connection is built only between the posts specified explicitly in the API call - not between their translations. Is this intentional? If not, how to trigger synchronization process properly?
If I create the connection via WP Admin UI, the connections get synchronized properly between all the translations.