I often read about getting backup from contractors for schedule information.  The following varies greatly, but based on a wide swath of the AEC industry contractors largely and commonly do what they want.  A large problem on large projects is getting enough bidders, and between that and needing to work with these same people again - much of the spec requirements is in a gray area.   For example, a contractor turns in a schedule with 5 long lead items with a contratrived duration of say 3 days float.  Close enought to the critical path that any minor set back will set-off a slew of delays.  Does an owner have the right to demand duration quotes from Suppliers?  Are these always in writing?  I have seen such delivers difficult to obtain.  As a scheduler, what commonly happens is the contractor PM or above talks to top brass and such requests go away.  After, 30 years - and working on both sides - I see contractors getting their way more commonly.  One thing that is common is the contractor making changes to the schedule spec in negotiation and it gets approved by people who have no idea if those items matter.