LASORS states confirmation of PIC U/S flight time is required prior to license issue (ATPL) which can either take the form of a letter from the operating company OR certification of each flight within the pilots logbook by the PIC, either is accepted.
For ATPL issue it also states (amongst other requirements):
250h PIC of aeroplanes required of which max 150 hrs of co-pilot time perfomed as PIC/US.
Whether they want this in the logbook as (signatures or no signatures) who knows. I'm now logging F/O time as either PF P1(U/S) under PIC hours and PNF as P2 co-pilot hrs whereas before I just logged it all P2.