Continuing to respond to myself...

Original fault code was 4208. Desert BMW looked at it again today and guess what -- fault code 4208 again.

They claim that is the code for the parking brake switch, but that obviously isn't the problem. So they installed a new EMF unit today and are reprogramming the X5 overnight. Current theory is water got into the area the EMF is in. They said they checked all of the wiring/harnesses were fine.

Wish I knew more about where the unit is and how the heck water could get into it.

Just realized if this repair fails, I'll be close to qualifying for the Minnesota Lemon Law. Brake issues are considered more severe in the MN Lemon Law.