Not true in my experience either. Obviously, photo contests need to have permission to at least use the winning pictures to promote the contest itself once it's over: to announce the winners, and maybe to advertise for next year's contest.
Some photo contests (I think it was Sigma and a few others at the time), say that they might use any of the pictures entered for advertising their products: for example a picture taken with a Sigma lens for the Sigma contest might appear in the follwing Sigma lens brochure, or Sigma adverts in the photo magazines. (Which is OK in my opinion).
I think it was O2 who did a "Travel Photography" contest a few years back – "any picture entered could be used for anything. Anywhere." More or less...
The first price was a Nikon point-and-shoot camera (hey - wow!!! Don't be too generous! What about a D2x?)
At the time, EPUK (Editorial Photographers UK) campaigned against that contest & as a result (though hesitantly) Nikon said they'd pull out of the contest until O2 changed the conditions.
I know that no-one is forced to enter a contest, and that we live in a free world.
But in my opinion, what BMW is doing is not OK. If they're cheeky enough to "ask" for unlimited usage rights of the pictured entered, at least they should emphasize that part of the contract a little more. Or give people the option: "You're not a winner, but BMW likes your picture – would you like to sell it to us?"