I called the dealership where I bought my first BMW, and spoke with the service manager. He used to date one of my close in laws, and they remain friends today. We've hung out before at thanksgiving and at party's before. Called him this am and got answers about his dealership.
BMW is not allowed to sell or promote any aftermarket products, they can only order aftermarket fluids if the customer demands them. His opinion is that he personally wouldn't use any of their products in his car, but there are a lot of ones out their that meet bmw's spec for each component. Said the BG products *should* be ok if there the right weight and designations. The only component he is absolutely adamant about using OE fluids on is the transmission. They strongly advise customers not to use anything but OE fluids in them. He has seen transmission issues come through with non common issues after aftermarket fluids are used. If customers are adamant to go aftermarket, he tells them to get the fluid from the manufactures of the transmissions ZF, and the correct designation for them. Said ZF sells fluids that are what he thinks are the OE supplier.
Certified cars are not allowed to leave the lot unless every fluid and parts are OE as factory. If there was not a mileage based service record at a dealership in the computer, all the services due based on the mileage of the car, must be performed using OE parts and fluids only. Obvious aftermarket parts like suspension components, pumps, alternators have to be OE also.
He did say that another local dealership uses a BG induction cleaning service, but they don't.
He said that the owner should ask for the 50k service record with the breakdown of the services performed and part number called out, and see what they noted used. Just for kicks.
TLDR: Service lead said that at his dealership, when a car is in warranty they are not supposed to use aftermarket parts (within reason) or fluids. Out of warranty they can, when asked (cost of part or service) they can only recommend fluids that meet or exceed BMW's specs. Certified car cannot leave the lot with aftermarket fluids or parts, they must be in original OE condition and all the mileage based services must be performed. He said the other local dealership uses BG for the induction service, apparently they have permission. If asked about reducing the cost of a service out of warranty, they can recommend fluids that meet each spec called out for, and he would never recommend a BG product, ever.