The pilot group does have input on the administration of PBS. Pairings are produced showing the days they work. You bid your desires based on a weighted system, 0 - 1000 points. You can bid specific pairings or types of trips, report time ranges, release time ranges, number of legs, length of legs, specific cities to fly through and/or RON. You can bid for TAFB or flight time. The variables cover almost every possible desire and it works very well.
I believe that because the most senior guys get exactly what they want there is more availability for junior guys to get what they want because, with line bidding, there is a certain amount one gets that they don't want in a senior trip which goes to junior pilots in PBS.
I was honestly one of the most bitter opponents of PBS when it came out but am now the biggest cheerleader. One of my biggest loves of the system is with vacation. I bid one week vacations on the very beginning or end of a bid period, then bid a string of up to seven days off leading into and out of the vacation. (seven in one month and seven in the other) I turn one week into three, four times a year.
I know the east pilots hate the thought of PBS and understand because I was in their place hating it at one time. I believe they would come to love it as much as the west pilots do if they would just educate themselves on it.