I believe they only truly check brake thickness and tire tread depth. They then go by the computer for brake fluid and oil change requirements. Anything else has to be painfully obvious to repair/replace during the CPO process because it comes out of their pocket. If they can get away with it and you take delivery/drive off the lot then it becomes a warranty repair that BMW pays for.

__________________
Current BMW's:
2013 E70 X5 xDrive35i Premium (mine)
2014 F25 X3 xDrive28i (hers)
Past BMW's:
2001 E46 325i
2001 E46 330ci
2003 E39 525i
2006 E53 X5 3.0i
2008 E70 X5 3.0i
2014 E84 X1