I believe the way it works is this:
When in reverse, the default is rear view. You can toggle to top view by selecting the top left icon (press the controller).
If you just press the lower left button in front of the console, top view is the default, but you can toggle to rear view.

The other icons enable the lines in the rear view.

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Richard
Sir Snaps-a-lot, 9 Time Dragon Slayer (54 runs!)
2011 X5 50i Alpine White, Biege Nappa /Lt Poplar M Sport
2009 Z4 35i, Black Sapphire/Ivory-Black/Anthracite

Gone but not forgotten: '08 550i, '06 X3, '06 650i, '02 M5, '99 540i