Basically you have the general gist of it.
We have a seat on a fleet. Ala 767A and 767B. Both of those have about 400 or so pilots each in ATL.
Now each month we bid in PBS. They send out an estimated line count for the month. This is hard lines with trips. Now we all go in put in our 75 requests and it spits out lines. (Lines Of Time~LOT)
Now the estimates have been way off the last few months. As much as 15 lines in each seat.
Now if you do not get a line with trips on it you are banished to reserve. Now we bid our reserve lines the old fashion way. There are bid packages in the electronic forum on the Deltanet. You bid these lines as we used to bid hard lines in E-Crew. (Basically if you do not get a LOT the PBS software directs the program to look at these requests).
Now the ins and outs of the reserve here are much like NWA. We have 12 hr long call and "reasonable time" (2 hr-ATL 3~hr in LAX and NYC) short call. Now the big difference here is that you do not bid for long call or short call lines. Per the PWA it is up to the schedulers discretion on how many and who gets short call on any given day. (Personal experience recently has been if I cannot fly a trip 28+ hrs flown already in a week they put me on short call. Now in the winter this is a lot different)
Basically on the international categories where Short call is a 24 hr straight period, you will get one long call day followed by a short call day followed by a long call day almost all month long. Domestically they basically do whatever they want and it depends on who is working that day. The short of if is if you sit reserve you will need a crash pad. Short call domestically is a 12 hr period that can start whenever the scheduler wants it to. The only requirement is a nine hr rest break before and after the period.
I have been used with as little as 1 hr left in the call window. As long as you are legal under Whitlow you are legal to do the trip. There are a good amount of pilots that get long call on any given day as well. Problem is that you will not know for sure until 3 PM the day prior.
All and all it makes a great case for being junior on a big piece of equipment and living in domicile. I know guys that commute to reserve and they are not home too much.