The government didn't just use TETRA; they engaged in enormous theft through software piracy, copying the software tens of thousands of times in a government data center. They destroyed evidence to cover their tracks, and now they're refusing to pay. Worse still, they greatly benefited from this illegal use, reaping significant advantages from TETRA's capabilities.
Moreover, they leveraged TETRA's success to release billions in government funds that had been blocked by Congress due to years of failure, turning their crime into a key that unlocked massive financial resources.
This is a blatant case of profiting from theft while evading accountability.