You are correct - CPO's are transferrable and can be brought to any BMW dealership (don't know if it applies only to the country it was purchased though). I don't know about the topping up of oil though as that would be a consumable item and not a warranty matter. If it was warranty isn't there a deductible that you need to pay for each visit?
'05 GMC Sierra SLT Z71 CCSB 4x4
'00 740i Sport