And, just for the record: as demonstrated by my own tests, and Raceboy's inspection of the schematics, the WWAN slots on X60/s/t have USB lanes only, i.e. true mini PCIe cards like most WLAN cards, the Broadcom Crystal HD, etc etc will not work in the WWAN slot.
(Also, I really should have removed all the old solder on the standoff pads before soldering the standoff on...





