I just had my lease-end inspection completed (Friday, 6 Oct 2017).
I chatted with the guy who did the inspection about what to do about the tires. (The pair presently on the rear had worn very quickly when they had been on the front, such that both rear tires were about 2/32" tread remaining, while the front were both at 6/32".)
He said that this condition would be clearly captured in his report and that someone else would make the ultimate decision about whether or not I would be responsible for any remediation. He said he'd been doing this for many years and had heard from many people that things didn't always go as expected, such that he STRONGLY advised against doing ANYTHING about it until I got the final report.
I got the final report the next day. While it accurately & clearly indicated the condition of each tire, it ultimately concluded that the condition did not represent EXCESS wear and tear, such that I would not be responsible for any expense associated with this condition.
Note: 45,000 mile lease (with 43,000 miles on the car) and this was already it's second set of tires.
There was an "asterisk" note on the report indicating that tire wear was something that might be revisited if wear was too far below 1/8" when the car was ultimately returned. I spoke with the MBFS folks at the dealership about this, before returning the car, because the way the note was worded made no sense in the context of my car's documented condition (i.e., already worn below 1/8"). They indicated that, in general, no one from MBFS ever looks at the tires again because their condition can be readily inspected by buyer at the time of auction (such that there is no "hidden" liability).
I returned the car to the MB dealership a few days later (Monday, 9 Oct 2017). The same MBFS guy completed the transaction. Other that checking/recording the odometer, nothing was said about the condition of the vehicle.
I'll update this if anything changes on the subject.