The Air Force and prime contractor Lockheed Martin plan to spend six to nine months checking out and testing the satellite and another six to nine months testing new ground systems before the spacecraft is declared operational.
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The $529 million GPS 3 satellite is the first of 10 being built by Lockheed Martin. The company holds a second contract, valued at up to $7.2 billion, for up to 22 additional GPS 3 "Follow On" satellites providing even more accurate, more jam-proof location, timing and velocity data to all branches of the military. Lockheed Martin built 18 of the 31 satellites in the current GPS constellation.
https://www.cbsnews.com/news/spacex-launches-air-force-gps-satellite-today-2018-12-23/
Willing to bet it's operational already, for MI use.