A story from HeatSt.com that was published back in November 2016 appears to lend some validation to Trump's claims that Obama 'wiretapped' Trump Towers during the election. From the story:
Two separate sources with links to the counter-intelligence community have confirmed to Heat Street that the FBI sought, and was granted, a FISA court warrant in October, giving counter-intelligence permission to examine the activities of ‘U.S. persons’ in Donald Trump’s campaign with ties to Russia.
Contrary to earlier reporting in the New York Times, which cited FBI sources as saying that the agency did not believe that the private server in Donald Trump’s Trump Tower which was connected to a Russian bank had any nefarious purpose, the FBI’s counter-intelligence arm, sources say, re-drew an earlier FISA court request around possible financial and banking offenses related to the server. The first request, which, sources say, named Trump, was denied back in June, but the second was drawn more narrowly and was granted in October after evidence was presented of a server, possibly related to the Trump campaign, and its alleged links to two banks; SVB Bank and Russia’s Alfa Bank.