The broadcaster, which was to show a documentary on the killing on Monday, said it had obtained copies of mobile phone and other communications in the case.
Other unconfirmed media reports have said the UN tribunal will announce indictments against Hezbollah members before the end of the year.
Hezbollah, which is close to Syria and Iran, has denied involvement and called for a boycott of the UN investigation.
The Shiite Muslim group is part of the national government led by Hariri's son, Saad. Lebanese politicians have expressed fears of a new eruption of violence in the country if Hezbollah members are charged.
Michael Williams, UN special coordinator for Lebanon, said last week that he expected indictments to be issued "in the coming months" but said he was also worried about the tensions.
CBC said investigators called in a specialist British communications company which found that the holders of eight mobile phones had been monitoring Rafiq Hariri in the weeks before his death.
A Lebanese detective had already uncovered the network and linked it to Hezbollah, the report added. The detective, named as Wissam Eid, was killed in January 2008 after he had sent his information to the UN investigators.
CBC said the UN team believed their inquiry had been "penetrated" by Hezbollah and this had led to the death of the Lebanese policeman.
CBC added that the investigators also suspected Hariri's chief of protocol, who is now head of Lebanese intelligence, had colluded with Hezbollah.
German magazine Der Spiegel said in May 2009 that Hezbollah was implicated in the Hariri murder through the discovery of two linked networks of mobile phones.
The magazine also said that a Hezbollah commando unit was behind the killing of Eid.
Disputes surrounding the special tribunal's work have caused widespread fears that new turmoil could erupt in the country.
The UN Security Council recently released a statement calling for the investigators to be left to work independently. This was reaffirmed by the United States on Thursday.
US State Department spokesman PJ Crowley said the tribunal's work "is critically important to Lebanon’s future. Lebanon needs to end this era of impunity which has afflicted it for years if not decades and we support the work of the Tribunal."
"I don’t think we are concerned with the objectivity of the tribunal’s work. We are concerned about the campaign that is going around surrounding the tribunal to politicize its investigation and its potential findings," Crowley added.
A UN spokesman said however: "It is a matter of concern that the leaks could have an effect on the substance of the work by the prosecutors and the tribunal itself."
"Certainly leaks are matters of concern. We want to be able to ensure that the special tribunal on Lebanon can go about its work without hindrance or interference," the spokesman, Farhan Haq, told reporters at UN headquarters.
He would not comment on details of the CBC report but said "we continue, of course, to fully support the work of the special tribunal and the independence of the special tribunal and its prosecutor."
The United Nations has asked CBC to give information on the documents it obtained "so we can assess them," Haq added.