Line 1 is even more interesting as it was converted from manually driven operation to fully automated operation without without major interruption to passenger traffic. (https://en.wikipedia.org/wiki/Paris_M%C3%A9tro_Line_1)
And it was considered successful enough that they've started work on converting Line 4. After line 14 was put in service in 1998, RATP actually started drafting plans to convert lines 1, 4, 6, 7, 9 and 13.