My dos centavos, for what's it worth and having sailed out of Vancouver twice in the last year:

When you arrive at Canada Place, you go through security first. Both times, we were in the same security screening area with Holland America Passengers. Each line had their own queue. On our May 24th trip, there was a sign that said Regent Boarding at 12:00. We tried to see if they would take us earlier because we were travelling with a disabled person in a wheelchair and were told that all passengers boarded at 12:00. At exactly 12:00 we went through secruity.

Once you pass security, you have go to thru U.S. customs (it is U.S. Customs, not Canadian, trust me). At this time, you will "converge" with other cruise passengers, there are no seperate lines for the cruise lines; everyone has to stand in line (and it does get busy). The first time the area was so busy we had to go sit down until called up by border patrol. We waited for about 25 minutes. The second time, because we were travelling with a disabled person, we were given immediate clearance to see the agent.

ONCE you pass these two checkpoints THEN your Regent experience begins...you walk towards the Regent registration area. I never noticed a special "AMEX platinum line" but since we have never waited either time it made no difference...we just walked right up to a cheerful face and within 5 minutes, we were on our way to the Mariner.