We were alllowed to do single channel CAT 2 approach in the classics because the A/P can remain engaged till 50 ft AGL . (JAA) Acording OPS 1 you have to keep the A/P engaged till 80% of the minima => 100 RA X .8 = 80 ft where you had to disconnect and perform a manual landing if you have visual reference. Boeing introduced new limitations for CAA registered aircraft that in my opinion make no sense, but that's other story.
Regarding NG , MUH (minimum use height) of the A/P single channel is 158 ft => NO single channel CAT 2 approach allowed.