In the domain of politics it is presumed that surveillance
the monitoring of behavior, activities, or other changing information
for the purpose of influencing, managing, directing, or protecting
people. -Surveillance Studies: An Overview. by David Lyon (2007).
is ongoing continuously, both from within and without.
As the technological capabilities currently exist, it would also be politically practical to presume that all communications are either monitored in real-time; recorded for the potential to analyze at a later date, or be used for parallel construction (e.g., "we already have the data, we now want to use the data as if we acquired the data in a different manner, or post-date the data as if we only acquired the data after a warrant was signed by a magistrate or judge"), possibly for a purpose other than the original scope or goal of the initial surveillance.
Given the above realities as to surveillance and signal monitoring capabilities, the topic of "wiretapping" depends on to what the goals and interest of the entity which engages in the surveillance are. Whether a warrant is required to "wiretap" communications is debatable; as technically that already occur(red|s) at a global level, without a specific "warrant" authorizing said "total information awareness".
The entity which is engaged in the surveillance could decide to use warrants or other court processes as tools to pursue the stated goals of surveillance of the specific target on the "public" record; or use the gathered data as leverage in a "private" political deal.