36,000 employees in the U.S. While the DOJ has already approved T-Mobile's reverse merger with MetroPCS, the FCC hasn't and the agency has been petitioned by a coalition in Congress and by the CWA which warned Congress that the merger could lead to substantial job losses.
Since the resulting company after the merger will be traded publicly, T-Mobile will have to answer to public stock holders. This means keeping costs and headcount down. Previously the company was owned by German telco Deutsche Telekom which will own 74% of the combined companies after the deal closes.
source: SeattleTimes via TmoNews