Does deduplication happen also on different repositories at the same server?

I have in my LAN one host running rest-server.
This rest-server holds different repositories for different users.
The structure looks like
/REST/user1/
/REST/user2/
/REST/user3/

Q: does deduplication also happen between the different users? I.e. is the identical file fileXVZ of user1 and user2 only backed up once?

No, those are not being deduplicated.