No, the offer for source must be to anyone -- the supply of a binary may be limited. BMW cannot be the "sole owner" of the copyright -- even if they own the part they wrote, they must still supply source for the GPL parts.
Source: https://www.gnu.org/licenses/gpl-faq.en.html#GPLRequireSourc...
BMW does not have to provide the sources to everybody. Only to its users.
edit: tzs also has a point. Hm?
https://www.gnu.org/licenses/gpl-faq.en.html#WhatDoesWritten...
Which sounds like if you didn't provide the source with the program up front then you're required to give it to anyone that asks since they may have received the program indirectly.
Which is rarely possible for a car OS, honestly.
Please specify a use case where you received the software without the VIN, thanks.
At least in Germany – and BMW is German.