What are the chances of degree revoke if an unrelated plagiarized paper was published during the course of Phd studies
It can happen.  But it would depend a lot on the policies at that institution.  As reported in the New York Times, consider the case of Senator John Walsh (D-MT), whose master's degree from the US Army War College was revoked when it was discovered that he had plagiarized a paper he'd submitted in partial satisfaction of his degree requirements seven years earlier.  They even ground his name off the bronze plaque listing the school's graduates.