Well, that's a bold legal strategy if true -- I wonder why Microsoft simply didn't put it in the Windows license agreement that government users couldn't sue them for antitrust violations!
(Uber's real argument seems to be "it violates our terms of service for a government official to try to figure out if we're following the law")
a) exempting themselves from specific laws by EULA generally doesn't work,
b) you can block specific people from a service and even police have to leave when told (barring further e.g. probable cause), but police are under no obligation to honor a general "no police" policy.
It's legal, though, to kick someone off a service because you think they're a cop. (e.g. biker bars that kick people out on that basis)
(Uber's real argument seems to be "it violates our terms of service for a government official to try to figure out if we're following the law")