Bidding

[ESpirit]

I am conducting research on bidding systems within fire departments. Any help with answering these questions would be much appreciated:

What kind of bidding is done? Vacation? Overtime? Position?
What is the bidding period for any of these? Starting and ending month?
How many man hours/work hours would you estimate it takes a department to complete a bid?
How common is it for departments to buy back vacation time?

Thanks.