BMWNA (for US customers) is different than the ________ BMW dealer that you purchased your car at. The dealers are franchises, so while they are mandated to meet certain criteria to keep the franchise they are not directly responsible for the warrantee and contract that you sign with BMWNA.
In case you wanted to know why a dealer won't mind looking at something under warrantee its because the dealer gets paid for the time and parts from BMWNA; the back end infrastructure for service is networked together with all the other dealers and centralized at BMWNA. This means that BMW knows how much work has been put into a car, parts, etc. and can then pay it to the dealer. This is the best practice because it allows the end consumer to bring their car to any dealer and access the files, ensures that BMW isn't being ripped off by shady service departments (I know those don't exist, at all, ever...)
'12 335i Sport Apline White w/black... Totaled
'14 535i xdrive M-Sport Carbon Black w/Mocha Nappa