Pitch lock usually occurs because of an oil problem, but once pitch locked the fuel governor controls rpm with in power authority, at 14330 to 14530 rpm.
Standard prop governing is 13820 +-2.
So if power is reduced to below 13820 that is when the 5 and 12 stg bleed could pop and then Brown is in rotation unless they are are feathered.
I am glad I was not on it having only seen one PL in about 4000hrs, and it is scary.
A good job done by a couple of Chaps.
BBG