lpates, yes of course you can log PICUS once you have finished line training, typically you would get half the total flying, since you will be PF for roughly half the time. That allows you to get your ATPL, but you still don't have enough hours to meet the oil company requirements for command (3000 hrs total I think) until you have been flying for at least 4 years.
Just to add one thing here - you need the Commander's sig. in your log book to count it as PICUS (at least as I remember) - there are some other requirements too but can't remember them off the top of my head. Either way, that means PICUS at the discretion of the A/C commander - so while you may be the handling pilot for some portion of the flight, if the commander isn't interested you cannot log it as PICUS, just P2.
And to answer my own point, this is one way the issue of FO progression can be addressed - assuming the Ops Manual allows for such a thing...
BG.