Friend of mine with a now defunct 737 operator had 6000 hours as first officer. Whenever it was "his leg" most times the check captain would swop seats and let him operate from the LH seat and fly ICUS. He placed that in the PIC column without any requirement to have the captain sign his log book entry. When the airline went tits up, he got a job in India as an direct entry command on the 737 and has never looked back. The Indian CAA apparently didn't look too closely at his log book as they assumed his ICUS time was real PIC - and who was he to contradict them?
The moral of the story is you should log as many hours ICUS as possible as it could one day get you a captain's job in a third world country.