As regards Trump tower, in the Obama DoJ, a warrant would not necessarily mean probable cause. FISA courts routinely rubber stamp government requests and they operate under what amounts to a reasonable suspicion not probable cause standard since their goal is surveillance and not criminal prosecution. In fact it is routine for the FBI to use gleaned intell not to prosecute, but to open the door for traditional gum shoeing in order to then wash the intelligence gathering out of the eventual prosecution in order to protect sources. In fact this was in the news jsut the other day in Tacoma Washington when the state supreme court ruled that Tacoma PD did not comply with state records laws. They had concealed the use of a cell tower stinger per an agreement with the FBI and did not disclose it to the defense.