I know nothing about Magnusson-Moss act, but i dare you to try. I can assure you there is not 1 hour warranty or return options for electronic parts if you take it out of the dealer not installed. There are a lot of electronic parts in the transmission, so in a case of failure it could swing either way. BMW will claim it was programmed incorrectly when first installed and nor Magnusson neither Moss could prove the opposite.
Everyone is free to believe what he wants, i just like to warn you that these are not all unconditional warranties.